I am afraid that there is no alternate source for these plates. The screw cap system , I believe, was patented by the canadian company NEXTAL that was then assimilated by Q...N and the patent is probably still holding.
Pascal
-- Pascal F. Egea, PhD Assistant Professor UCLA, David Geffen School of Medicine Department of Biological Chemistry Boyer Hall room 356
611 Charles E Young Drive East
Los Angeles CA 90095 office (310)-983-3515 lab (310)-983-3516 email [log in to unmask]