I have only had one go in heat, had the others all spayed at 6 mos. but, I had a shih tzu years ago, and I bought her these little panties they make for dogs. Can't remember where I bought them at though. I'm getting another puppy the end of the month, and since she's so tiny, I won't be having her spayed until she's around a year, hopefully with her being small, she wont' go in to heat until after that..good luck on your search..I'll have to check back and see if anyone has any answers for you..Well, how about something like these??
PetEdge: Clean Go Pet Female Pup Pants