It is Tygon tubing that Rob uses, the same stuff that everyone water cools their PC with.
You can get it here in any ID/OD you want..
Tygon R-3603 PVC Laboratory and Vacuum Tubing, Clear: Industrial Plastic Tubing: Amazon.com: Industrial & Scientific
I don't think that's the same as Rob uses - this is PCV, and he uses the silicon tubing - I think it's tis one:
http://www.amazon.com/dp/B001CLO08Y...TF8&colid=2708HJRRVKUZO&coliid=I2Y1149RBYCV15