Undershirts?

I am a nursing student and just got my first pair of scrubs (yay!). Anyways, we have to have a certain color (burgundy) while we are students I learned really quickly that they show sweat marks like crazy. I a moderate sweater and worry about sweat marks. Especially now because it's coming up on summertime and the school keeps the building quite warm. In the past I've just bought a set of men's undershirts to put under my uniforms and used the clinical strength antiperspirant but it hasn't always been enough in the summer. I've run across several sites offering specialized undershirts and pads you can sew into shirts but I'm unsure on what to purchase. I have limited funds and don't want to go out and spend a bunch of money on something that's not going to work. Can anybody suggest any ideas or products that work?