I dove in the subject as well. I am pursuing the FAA flight navigator certificate. I purchased an A12 bubble sextant on ebay and a Polhemus celestial flight computer.
Aircraft Bubble Sextant Link A 12 100 Reconditioned and Ready for Use | eBay
The sextant I received from this genlteman is in perfect condition with all the parts. You won't find a better sextant than that. There are many out there but be careful, a lot of them don't have the bubble or are just simply missing parts. The Polhemus flight computer is similar to an E6B but designed specifically for celestial navigation. It allows you to obtain essentially almost all your corrections by setting your course, latitude and estimated groundspeed and this without having to open one book. On the other side of it, you can use it for plotting your line of positions. It makes celestial navigation so much easier.
You will still need the Air Almanac (not the one published by UK - it's missing the navigational data) and the H.O 249 sight reduction tables.
Keep in mind that celestial navigation for aviation is slightly different than maritime. The concept is obviously the same but the technique is I would say very much different.