Impossible

I fancy myself an active pregnant person -- at least since I've been feeling better.  But there is a hitch: apparently pregnant people aren't supposed to be comfortable whilst being active. I have searched for pregnancy yoga wear, and despite the 3 million prenatal yoga DVDs on the market, I can't find an appropriate  tank top anywhere. They're all super low-cut (which borders on the obscene during a good downward dog) or $60 (hey, I like yoga, but I'm still cheap).  T-shirts are okay, but clump after a nice sun salutation, requiring constant adjustment (a real downer during a relaxing practice).  What is a poor pregnant yogi to do?