two ways to do it:
Cheapass redneck engineering method:
take one of your barbs to the hardware store (big box store may work best for this), find the guy who sells the tubing. Not the pimple faced teenager, the old guy who actually knows what is in the department and what the stuff in it is used for. Show him the barb, and tell him you need tubing that will fit on that barb that is non gas permeable and will resist temps of 75c. If he doesn't have any ask where you can buy some. You will need that, a bunch of hose clamps, and a jug of deionized water. Also a bit of silver wire maybe 2-3 inches long. (dunno where to get that in your area, we got a jewelry supply shop called the silver toolbox here, but you may have to go to a custom jewelry maker or go online or something.
The silver wire gets coiled up and wedged in the tube to act as a biocide. There are other ways to do it, but the silver doesn't need to be replaced.
get a ruler and find out what diameter your tubing is the OD (outside diameter) of your barb will be the ID (inside diameter) of the tubing you need. It should be something like 3/8" or 1/2".
Get online, and look for water cooling tubing. There are a bunch of stores and vendors that sell it. There is a whole section in fact in the forum. NZXT, frozen CPU, etc... I don't Pay attention to the brands myself, but you can get all kinds of advice in the water cooling forum. You can pick the color of the tube, the color and type of hose clamp, whether the tubing is clear or not, The color of the fluid, the type of fluid etc.. You can make it all very pretty.
Personally I prefer the redneck engineering method because I have no desire to gaze into the bowels of my computer, and don't hang out much with people who would be impressed by it. I just build it ugly so it works and I don't have to mess with it. You have a big peekaboo panel on that thing, so you don't have a whole lot of choice int he matter. Either way works. The boutique method will get you tubing that is easier to manipulate, which is a slight advantage. The prices will be significantly higher though. Or at least were the one time I looked.
Edited by bombastinator - 11/17/13 at 3:05am