You're going to need to bring at least 2 ounces in with you.
If you don't have big gazungas, this might not work for you, but here's what worked for me:

I just filled two 1-ounce Visine bottles with clean friend pee, got sticky Heat Therapy Patches from Walgreens, put the Visine bottles in a pair of latex gloves (just so I'd have the gloves...I don't want pee on my skin), put the wrapped Visine bottles against my skin (under boob), then put the Heat Therapy Patches (sticky-side against skin..watch for nips!!!!) over the bottles under a well-padded bra. At home when I tested the temperature without the heat patches, it had been a couple degrees too cold.

If I ever have to do this again, I will not bring in a cheapy thermometer (it didn't even work right!), but I was very concerned about a beep. Luckily, I was doing a Rapid Test, so the temperature was only checked by the little indicator on the side of the cup. You've probably seen some of the same articles on substitution as I have, but the best piece of advice I got was PRACTICE! That's how I was able to work out the kinks and figure out the most comfortable way for me.

Good luck on this!!! :thumbsup: :jointsmile: