Plenty of strait guys are into anal. Look how incredibly popular pegging has become in the last couple of years.
Sounds like you might just have just got used to the butt plug, that can happen if theyr small.
If you want a p spot dildo, anything that g spots as long as its anal safe (eg. With a flared base) will p spot.
Size wise, you want to pick a dildo smaller than the largest size of plug you use. Theres no neck on a dildo, so theres more stretch and the thrusting motion is harder on the sphincter muscle. So sizing up slowly is important.
Alot of the guys on here swear by the njoy pure wand (its famous for a reason) but it is expensive. So if you dont want to spend that much, there is a glass dildo on the shop with a similar shape that is a really cracking g spotter and slim. ((Review here)
Im sure some of the guys will give some good recommends, but looking through the slimmer dildos and reading the measurements (especially the circumference) would be a good place to start. If your not up to the right size on a plug you may need to work up a plug size or two before getting a dildo.
This is the bit you want to make sure to read. The measurements, especially the circumference and length and really important for anal play
