Just so you know...there is no cache of women who are eagerly waiting to take the cherry of any offered up virgin ass that is craving a pegging. It simply does not work that way.
If you just want to experience pegging, go find a sex worker to help you. And I am serious about that. Sex workers would love to have a nice clean and respectful man who wants to experience pegging pay them for services. Depending on where you live in the world, it may even be legal.
If, instead, you are looking for a relationship with a woman who will peg you, then look for a woman in the way you would normally go about finding a partner.
If you want to be sure she's into pegging before you date her, FetLife.com is free and will connect you with kinky folk in your area. The search capabilities are definitely limited, but I believe that helps to keep out the riffraff. You can find people in your area, but you have to take the time to look at each profile to see their kinks. (There are other dating websites that cost that will sort by kink - but I can't recommend them.)
So let's say you find a woman you are interested in, you've read her profile and determined she is available. The worst possible way you can approach her is to say - "wow, you are into pegging, will you do me?" Do you do that in all your relationships? "Wow - you are cute, can I fuck you?" No - you get to know her first!
Have some respect and manners in your approach. Send her a polite letter of introduction and engage her in conversation about something other than pegging. Meet with her over coffee, take her out to dinner. Get to know the woman, don't just pursue the strap-on.
I feel for you, guys...and I'm honestly happy you are interested in pegging, but start thinking with your big head!
And don't forget - it is indeed possible to turn an open-minded woman who has never done pegging into an enthusiastic pegger. I have heard many first hand accounts that bear this out! For some advice on how to do that, read this:
For one man's story on how he turned a vanilla girlfriend into a pegger, read:
Best of luck with your search, gentlemen.