Scytek doesn't make them anymore, but Biocare has them, in slightly different
design, but you might be able to get just the slide holders and lids
without other bells and whistles that have been added to improve their
usage.  HOpefully, they would sell you just the part of unit you need.

I have several, and prefer the old design with all clear plastic lids and
not the windows on tops, can view the slides sooooooo much better that
way.  Even so, they are sweet!

Gayle Callis