The valve has traveled with an empty box, a bottle was purchase, fish packaged and the valve and fish shipped back.
Here is the best deal I've found but I did not purchase it from them:
Oxygen valve for disposable red tanks from Home Depot.
All mine came from craigslist. Both the beer version and the real cylinder/regulator. The later is much more cost effective in the long run but you can ship or travel with the little valve and get the oxygen at any hardware store.
For the main tank I got one of these (minus the regulator):
http://www.aquaticeco.com/subcategories/1120/Air-Filling-Kits
Here are the two individual pieces:
http://www.aquaticeco.com/subcategories/1116/Air-Nozzle
http://www.aquaticeco.com/subcategories/2464/Oxygen-Hose
This seems to be the easiest/cheapest ($60) plus you have a cutter/brazer if you're into that sort of thing:
http://www.homedepot.com/h_d1/N-5yc1v/R-202185043/h_d2/ProductDisplay?langId=-1&storeId=10051&catalogId=10053
