Seriously, just be yourself and personally I would be upfront as possible about the ostomy just as you would be with being a single parent. That filters out the losers right away without any hurt feelings.
Good luck to you
Ive been In 4 relationships in the 18 yrs since my surgery and I ended things each time, none of the Ladies had a problem what so ever with my bag. most of the time we are the with the problem of feeling different. I'll be the first to admit I've struggled with self esteem issues, but each time once i saw my partner didnt have an issues with it -then my issues went away.