You use the pftek for your mycology?
i never found any i resorted to 5 gal plastic lids from home depot 98cents ea. now i have heard of trays made for washing machines , they are supposed to be like 3'X3' , but like i said i didn't find them ,good hunting will stay subed to see what you find out .....rob
HTGSupply.com (high tech garden supply),<- heres my preferred source. They have 4-5 retail stores on east coast, I drive 2 hours to the closest one...
if you dont mind round pans.....home depot had fairly large round plastic pans to put under waterheaters. They even come with a fitting to set up drainage.
The lowes trays work ok, they dont drain well for flood/drain applications. Make GREAT growing beds or hold two-three slabs..