I have expressed my fantasy of watching my wife with another man. Which she explains that she has no interest ( which I respect) But she is open to finding ways to fulfill with toys and such
I guess I’m looking for advice, techniques and toys, to try and make this fun for both of us.
@Deecoy - I don’t blame your wife as the idea sounds fun but often leads to disappointment if other troubles
I suggest role reversal- you are submissive and she dominates you - try pegging / cross dressing and spanking
Bondage is another great idea with sexual teasing where she winds you up to bursting point but refuses to allow you to cum
Welcome to the forum - I hope you pick up some great ideas 
Right there with you. Realistic dildos are a start. I got one and really enjoy teasing her with it. I just signed up to test the SILEX-D Apollo L Realistic Torso with Interchangeable Dildo 7 Inch. Watching her ride that would be a lot of fun!
It’s fantastic that you’re diving into fantasies together! Since we’re having so much fun with role-playing, it’s a great way to explore those desires. I absolutely love the Black 9.5’ King Cock suction cup dildo from Lovehoney— perfect for giving my husband a show. I let him pick one out for me, and he’s thrilled watching me ride it. Sometimes I even send him steamy pics while he’s at work to keep the excitement going 
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We also spice things up by describing our “ideal man” while I’m pleasuring him or reminiscing about past encounters. It’s all about making the fantasy come alive and keeping things naughty and exciting.
The love honey real feel 8inch dildo is amazing. I love watching her take it as it’s bigger than me and she likes it for the same reason . Depends on your size and what she is willing to take. My advice from doing this is the higher she can take compared to you then the naughtier it is. Also we have a cum squirting dildo she loves using it then shooting the cum inside her and she is all loose and we imagine she’s just been taken by a hung guy and she’s all lose when I then have sex with her
How about a fking machine
U can pick them up quite cheap if you look.
Don’t stick with the default accompanying dildo either, they’re usually crap.
Get a suction cup attachment, and then you have the choice of lots of dildos, like others have recommended on this post.
Im sure theres realistic dildos which you could choose together to add realistic image for you, or theres plenty of other dildos on the market.
Depending on what you want to watch as well, remote controlled / app toys so you can control the vibrations whilst watching, su tion cup dildos coukd be attached sonewhere and you can watch her ride that rather than her manually inserting the dildo…
It depends on how you want it to look, also what your wife would like, spend the evenong shopping on LH to find what tirns you both on for this fantasy
A realistic dildo may be a simple solution, but don’t assume she would go for it.
In my experience (trying to get my wife to suck on any kind of dildo, let alone a realistic one), there is a bit of a psychological barrier that stops her wanting to do it. While I would be turned on by the fact that it is half way to her enjoying another cock, it seems to turn her off for the same reason.
For her, fantasising about something or simulating it is not much different to actually doing it, so it’s a big step.
So there may be a much more complex issue about her becoming relaxed and comfortable about fantasies that you will have to work on.
One thing is for certain: you have to make it clear to her that you are looking for a substitute for (or simulation of) your fantasy, not practice for it, and you have accepted her decision not to do it for real as final.
You could create a dummy additional man in your bedroom using your clothes then add a larger dildo than your penis. Your partner can then treat you as her cuckold ie you are the spectator watching her have sex with her other stud.
Of course this scenario will depend on your partner wanting to do this for you.
Maybe try one of them torso toys as then least it’s kinda like the fantasy 
Although there is some great advice on this thread, sadly, if your wife has psychological barriers that prevent her from wanting to part-take in your fantasy, you have to respect that. I have a major medical play fetish (probably for reasons that I can’t go into on the forum) but my husband has no interest in it at all - for him, it’s weird, unloving and unsensual, and involves a level of roleplay that he just can’t see himself doing. It’s a shame, because his Dominant self is hot and I think he could nail the “mad scientist” vibe without too much effort if he wanted to, but he doesn’t want to and so I have to respect that. A realistic suction dildo as others have suggested would be my thoughts too, but if your wife isn’t interested then you must respect that, as hard as it is to accept.
The one work-around for me is that I am non-monogamous and I have had a few partners who have enjoyed exploring my kinks with me in one way or another. However, that solution isn’t for everyone.
I wish you luck, however this goes 