what kind of tubing did you try? i wish i saved the pic when i saw it, but the tubing that guy used looked pretty flexible and he said it wasn't hard to get on there.

i looked around homedepot.com and found some pipe insulation that looks similar and might work. there are 1/2" and 3/4" diameters and it says foam in the title, but the material is listed as Polyethylene. search for "thermwell pipe insulation." i'll try to go to home depot on my lunch break tomorrow to see if it really could work.