The only option for fitting EPROMs to Acorn System computers is the single socket on the CPU Board or the two sockets provided on the 8K RAM 8K ROM Board, they never produced a ROM only board, the only other option is to use the Control Universal CUMEM Board. I do find though that I am regularly swapping out EPROMs e.g. to switch between COS / DOS or BASIC extension ROMs so decided to make a board that would hold several EPROMs with front panel switching to select what you wanted. So this board has ten EPROM positions and I also managed to fit in an 8K RAM !
There are four rotary switches on the front panel that can select the EPROM/RAM for each of the four 4K banks at C000 to F000 as follows:
S1 selects between two EPROMS at F000 (Banks 1 and 2) e.g. COS and DOS
S2 selects between two EPROMS at E000 (Banks 1 and 2) e.g. NFS
S3 selects between three EPROMS (Banks 1 to 3) or RAM (Bank 4) at D000 e.g. BASIC Floating Point Extension or ONLIBASIC
S4 selects between three EPROMS (Banks 1 to 3) or RAM (Bank 4) at C000 e.g. BASIC or ADE
The board only accepts 2532 EPROMS and not 2732 (sorry but that's what I tend to use on all my machines).
Fortunately I found the RS1010 rotary switches which are just the right size to fit four on a front panel and not expensive either, generally they are 2-pole 4-way but the other variants 1-pole 2-way and 1-pole 4-way are out there (on e.g. eBay).
They have a splined shaft, I couldn't find any suitable knobs so 3D printed some, here are the files:
Schematic
Bill Of Materials
Blank PCB
Front Panel Drilling