If you are really small, you could wear an underarmour (heat guard, I think) shirt underneath your shirt. You can even do a couple other layers-- for instance underarmour shirt, button-down shirt or underarmour shirt, t-shirt, zipper sweatshirt. Not sure what the weather is there.
BTW, you can substitute underarmour for any kind of compression shirt. Muscle shirts also give a bit of compression too.
I'd be careful with any prescription stuff. Of course in the US you can't buy it, but I know in the UK you could.
--Jay J