For any brewers new to Okinawa looking for a place to fill tanks, this is what I've found out. Okano Gas Company (link below) will fill your U.S. tank after it passes inspection. The inspection costs around $42 and takes about 3-4 weeks; it's good for 4 years. Once it passes inspection, you must pay an additional $6 for certification. Certification is good for one year and you must present it to Okano each time you want your tank filled. After the certification is no longer valid you just pay another $6 for new certification paperwork. It costs less than $20 to fill a 5lb tank.
As far as ingredients go, I'm ordering from Jasper's Homebrew and Wine Making (link below). They shipped after 1 day. They have a good selection of kits that they build once ordered.
There is also a local nano brewery; Okinawa Brewing Company. They may be willing to provide a yeast sample if you ask nicely, but I cannot confirm this (link also below). Their tap room opens the weekend of the 18th; located right outside of Torii Station.