You can buy Taiyo Yuden online from rima.com or supermediastore.com. There are undoubtedly other online stores with TY, but these two are known to be reliable outlets. Rima seems to be a little higher priced as a general rule, especially on shipping.
I would buy TY 8x +R disks and burn them at 8x. The white inkjet printable version will show fewer fingerprints, but is quite a bit more expensive than the silver laquer disks.