Where do you get them? Do they have to be food grade? (i'm making liqueurs).
You should use food-grade vinyl tubes, like those used in beer brewing and wine making. Not sure where you are geographically but northernbrewer.com has a good selection of these in all diameters. Look in the "equipment" section.
Midwestsupplies.com would work as well. For beer brewing you use a auto siphon (racking cane) that using comes with siphon tubing.