A washing machine drip tray offered an affordable solution - problem was the raised centre section and what to do with it..? If I left the press squash it, it would most likely crack... so:
...armed with some cash I paid my local Direct Plastics a call. I got some sheet for an infill...
carefully cut base infill
...same again on top side
Hole carefully drilled
to take Vit C tube
being carefull it's a tight snug fit
and finished job
and in use with newly aquired plastic food tray bases (though I could only obtain 5 so still need plywood racks...)