Search the CONFOCAL archive at
http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
go to www.newegg.com or www.cdw.com or similar sites, or the electronics section of www.amazon.com and search for
parallel port card
$10 and up (but a lot less than $200). With more effort and money you can find multiport cards, i.e. 1 parallel, 2 serial, 4 USB2 etc.
Typically want to check what slots are available in the new PC. Seems silly to waste a PCI slot on a single (or even multiple) parallel port, but if it enables you to get your memory key working, go for it.
Your current USB to parallel port cable might just need some BIOS like tweaking, like bidirectional (EPP, ECP ... if I recall correctly).
best wishes,
George