For my press bed I went down to the local building center and picked up a sheet of 5/8″ particle board laminated front and back with melamine.
It just fits on the bed rollers. I think it will wonder side to side when I’m pulling a print, so I may have to build some guides.
Not sure how well it will hold up, especially when I start doing prints that require higher pressure like etchings. Still for the cost if it lasts a year I will be happy.