Try Grizzly Mountain Engineering - http://www.g-m-e.com/new_page_3.htm
Also try PBL http://www.p-b-l.com/pbl2002/fss-NA.html However Bob Longnecker passed away several years ago and they have discontinued production. I do not know if they are still repairing the PFM units or not.
If you have an old issue of MR, back when PFM was still advertising, call that number. I don't know if I am allowed to give you the number in this forum. One of the tecnitions that worked for PFM will answer and he still repairs the systems. At least he did for me two years ago. I don't know about the tapes, I think I bought the last set he had.
Try this link for new tapes. I can't find anyone who services or sells PFM systems, though, because they have been out of business for decades.
http://www.mail-archive.com/s-scale@yahoogroups.com/msg11607.html
Looking for someone who services and repairs PFM sound systems, also looking for new tapes.