www.mcmaster.com carries all the sizes you list in silicon. Look in rubber tubing. I also hear tygon is good, but it's a form of PVC, so I don't know how it affects UV.
Also for the Darkhorse, try calling your local semi-truck shop. it's common use is for detecting leaks in big trucks, and I got some for free from my local Peterbilt dealer. You only need about a drop per litre.