Bigger O Rings

Hey guys, first time posting and I'm here with a question, haha sorry!

I'm having problems finding an O Ring with the correct diameter for my strap on. I have the 8.5inch girthy 2.25c dildo from LH (which is fantastic, might I add!) but it seems somewhat impossible to find an O Ring that will fit around it so I can wear it. Is there any way to do a bit of DiY and make my own safely? 2.25

Many thanks!

We have two solutions to this - the first is a silicone cock-ring (the largest from a set from LH if I remember correctly) and the other is some metal rings I got from a leather craft place (I guess they were intended for making up horse harnesses or whatever but they do them in a wide range of sizes up to massive)