If "ordinary" 8mm Sony tapes (as opposed to "data grade" ones) are OK (I've used them for years, without incident, though the collected folk wisdom advises otherwise), Honest Ed's is a good source. Last time I bought them they were around $7 each, lots cheaper than other standard sources. (I've occasionally found them even cheaper at various fly-by-night places on Spadina.) Of course, our drive is an old 8200; dunno how they'd work in the higher-density drives.