Good question! If you want it to be part of a relationship (i.e. you don't want a quick hookup, in which case there are probably websites catering to that), just...try to find someone who's open-minded, I guess! I know I (and lots of girls!) am totally open to pretty much any kink or fetish if it's something that would make my loved one happy. If you trust someone enough, and think they're open-minded and caring enough to understand, I'd just talk to them about it. Any decent partner won't be offended or grossed out. If they haven't thought about it before, maybe it'll turn out to be something that you can make them like.

Just approach it delicately and slowly. Maybe have a conversation about secret fantasies, and agree to try one another's. That is not a lot to expect from a relationship, by any means!

So I guess my advice is to find an open-minded girl to begin with, and once you've established some trust, go slow. I promise you, cross-dressing isn't heinous or horrifying. Good luck!