I'd say go to your local reno-depot or plumber shop and buy your tubing there. I got 10 feet of 1/2 ID 5/8 OD vinyl tubes for 4$CAD. That's 20$ cheaper than "equivalent" tygon or whatever brand tubing (besides the fact that 1/8 thickness is rare to find online apparently).
Make sure you clean the Thermochill rad well before you use it with LOTS of bioling distilled water. If you dont, youll be breaking your loop down in a week to clean the flux from that rad out. Myself, Id just buy a cheaper Swiftech rad, that will cool as well with less cleaning not to mention you dont have to use some non-hetero fitting to get it plumbed up, it uses a g1/4 like the rest of the known world. http://www.petrastechshop.com/swmcqposerab1.html