Newport Glass has several sizes of refractor kits on their website. Sorry that I don't have the address but it's not hard to find with Google.
Refractors are a lot more complex in their design in that there are thousands of different glasses out there and you have to use the refractive indices for those glasses to figure out the curves you need to put on the various lenses that need to get made. This isn't difficult with today's software but it is a step that isn't done with reflectors. The actual glasswork is actually easier than with a reflector as all surfaces are generally spherical and can be made to a lot more liberal specs than a reflector is. Also, if you do have problems with a refractor design as to things like spherical abberations, you can refigure the lens without losing the functionality of the optics like you do when you silver a reflector and then find out that you need to do more work.
If you're going to use the Newport glass, use their specs for curves as they will do quite well enough but if you know of some glass somewhere, make sure that you know what the glass is or you'll have a pig in a poke and will have to do a lot of strange things to find out what you have. Undocumented glass is something that a lot of people have obtained for one reason or another and finding out what it is can become very difficult.