I know I joke about living in a bit of a time-warp in general, but the grocery store here definitely still sells blank cassettes. (But not spare DVD cases, which is what I needed.)

Also, shoutout to the other best ways to make mixtapes, which involve sitting beside your radio with record-play-pause pushed and very quickly un-pausing or the also-workable-with-dual-cassette-boombox 'record large chunks of radio repeatedly, snag the good songs out of that' method.

(I'll have to post some of these at some point, I do still have them...)