First, welcome. Second, many, many straight men enjoy anal play, and the community embraces that fact.
As for your question, I'd suggest a vibrator designed for anal play (do a google search). Go very slow, and use lots and lots of lube. There is no such thing as too much lube. If it hurts, you're not relaxed enough (relax and slow down), or you don't have enough lube (add more).
There's also a ton of great info on all things anal in "The Blank Manual" sticky at the top of this board. Good luck!
If you ever manage to achieve an anal orgasm please let us know how you did it. Sometimes I feel a sensation that's a bit like an orgasm building and I've always wondered if it's possible for your ass to have something akin to an orgasm. I've never managed it myself, I always wear myself out.
True, comfort is #1 in finding the right toy, but they never told me that vibes worked for men too... they really do... amazing. Just keep to soft things. And go slow.
Another thing, if you buy a dildo make sure it's not an "adult novelty item." They're often sold as sex toys but are made from a material that's not suitable for inserting. Make sure it's smooth to the touch.