This is a great thread D O, I'll be sure to rep you for it. I like the memories by looking at the rows of tapes and the video you posted talking about them. It's good to travel and visit thrift shops every now & then to take yourself from all this digital downloading madness we have today, it's a great way to experience life. I used to live in Cali, the Pasadena/West Covina area.
You should try going to record conventions to find tapes, check this calendar for upcoming US dates:
http://www.vinyltimes.com/record-shows.htm
Then there's people you should check outside the US who are collecting tapes still to this day, like a number of Japanese record stores and European hip hop fans on eBay. Soundtable Records in Japan was one, but their site no longer exists
http://mitglied.multimania.de/rapacent/newpage3.html
http://img251.imageshack.us/img251/1596/img0132jpg.jpg
I still cherish full ablums on tape, but the most favorite ones from my collection are the limited addition promo tapes and maxi singles with bonus songs. I used to hang out at a radio station in the early-mid 90's and the host would give me bags of promo tapes sent to him from labels.
Keep up the good work in this thread, I'm here if you need any info on NY tape spots.