Here's an idea.
1. Agree with your partner what you would like them to wear (be sensible here otherwise you could get yourself in trouble).
2. Arrange to go to a town separately so that you are both there at the same time.
3. Just walk around the town by yourself until you meet (no cheating! keep your mobile on silent).
4 Then when you meet up treat each other as a friendly stranger.
5. Go for a coffee and get sexy!!!
thank you guys. i will be making a trip to the thrift stores soon...
If you do a search online for plus size women's clothing, many carry costumes.
you could also do role play that involves minimal costuming. I have a fantasy I've been playing in my head about seducing a "stranger" in a bar. Or one where the only costume I need is a Apron, thing highs, and heels. If he has a tool belt or box, he can be a handy man/mechanic. Look around, you may already own things that you can use.
I like to dress and play the part of a high end escort, or sometimes the sluut next door
Female dressed as a cheerleader, male as the school principal. How about pirate and wench? Woman wearing only lots of jewelry and guy as the cat burglar, etc.