The NitrousWorks purge kit comes with a short length of copper tubing (smaller than 3/16", unsure of the actual dia.) and a compression style fitting. If you need a piece longer than what comes with the kit, I image you could find some at the local hardware store, along with the other necessary misc. fittings to run the dual outlet purge setup (if you want to).
Other than the above, it sounds like you've got everything covered... maybe a fuel pressure safety switch?
Oh, if you have a stick-car, I'd highly recommend wiring up an MSD RPM window switch that turns on/shuts off the nitrous system at a user specified RPM range. It'll save your head gaskets when you spray in first gear on radial tires and bounce off the rev-limiter!
It's one of the better safety items that you can use with a nitrous system.... nitrous oxide + rev-limiter = BOOM!!!
