How does a man find an anally receptive woman?
The answer is at once simple and complex. The simple answer is to be Prince Charming to a lonely woman. The complexity is that many wonderful women are lonely victims of the almighty Masculine Ego. Overwhelmingly, men seek out petite beauties as trophies to show off to their male friends.
In my personal and work lives, I have observed the ruthless shaming of non-conforming females, from childhood through old age. Most often, the cause is obesity, but it can be race, language, social class, or any characteristic that makes people, especially males, pick on them. From the onset of puberty, most overweight girls are starved for boys' affection and enter a downward spiral of plummeting self esteem. In their twenties, they often give up on ever being attractive and stop trying.
But they never stop wanting the love of a good man -- AND the life that comes with it. A reasonably eligible ass man who befriends a homely, overweight single woman will often notice a change for the better in her appearance and flirtatious amicability. If this man is you, this is where things get very complicated. I've said here and on other sites that anal is not for swingers; it's for committed, monogamous couples. Before you bring up the subject of anal sex, be sure you want to "get serious" with her, not just use her and then break her heart.
Keep in mind that she may have a history of being anally used. There was an academic study a few years ago that found obese teenage girls much more likely than other girls to have had anal sex. The apparent reason was to make themselves desirable to boys who were really just using them. How you deal with that history is up to you. She will need a lot of reassurance that you're not history repeating itself. One reassuring act would be to start introducing her as your girlfriend, and letting her reciprocate.
And the final complication. When your insecure friends snicker about your new girlfriend, tell them to shut up.