E-Bay. Yes, pre recorded R2R tapes are hard to find, but e-bay has a vast selection. While most are 4 track, 3.75 speed, the treasurers are 2 track, 7.5 speed. A while back a Miles/Blue of the latter vintage went for almost $2K. Barcley Crooker tapes, perhaps the highest quality of pre recorded tapes also are sought out. Some of the latter go for $50 plus, however most are classical titles. Another area of pre recorded tapes are 'broadcast' masters. Most come on 10 inch reels, and are 2 track. The best of these are AFRTS tapes produced by the government for the military broadcast system. I have a few hundred of the latter and quality is very high, our government produced nothing but the very best, after all it was using taxpayer funds. I have about 6000 tapes in my collection and enjoy them everyday. I have about ten working tape machines.