The FREDERIK desk used to be known as the
JERKER
(yes) and some of the options included the CPU holder that you see for $10 and I assume the same goes for the printer shelf.
There is a CPU holder currently available in the SUMMERA line that coordinates with GALANT - from the looks of things, you may be able to use it for both the printer and the CPU, but don't take my word for it...I'm just looking at pictures and guessing. Hopefully someone who has some experience with this item will come along and lend some advice.
Welcome to IKEAFANS!