Hackers help: IKEA BESTA DESK under desk extra shelf?

besta-desk

Materials: 701.166.53 BESTA Desk

Description: Hey guy, I need a little help here, I want to buy 2 IKEA BESTA desks, and add to one of them, an under desk shelf. It has holes for it, but I can’t find anything, that could fit there, maybe there some other BESTA item, that has compatible shelf?

~ Doni Mendel, Israel