Need Tee shirt Pattern for Doxies

Hi, I’m looking for a sleeveless teeshirt pattern for my Doxies - without the legs. Purchased tees never fit right, so I’d like to sew them. My girls are 15 lbs. and 20 lbs. and, of course, have very short legs, so it’s very difficult to fit them. I’ve found lots of patterns for coats and sweaters and harnesses, but no teeshirt patterns. I hope someone can point me in the right direction.
Thanks, MaryJane