I have a Tektronix pizza-box style case that might do, but the board needs to be upright for good convection cooling.
I have a suitable PSU .
The PSU connector is a 4-pin thing but Toby want £4 postage on a £1 part. So I may simply wire power directly in to save looking for the plug.
2019-02-10 Finding it very hard to get this board going. Managed to make a bootable DOS drive on CF card but this won't run the WinXP installation files in DOS mode. I think the only way is to get an IDE CD-ROM drive and boot from that. Perhaps borrow one from an old PC? It is cheaper in time to just buy one.
I have found an old external drive that takes in 12V and steps it down to 5V, then both rails go to a 4-pin Molex drive power connector. I intend to use this to power the optical drive while it installs WinXP. Afterwards it and the optical drive are no longer needed.
2019-02-11 Salvaged an IDE CD ROM drive from an old scrap PC. Did not work, nor did either of two IDE hard drives I had.
2019-02-15 Tried to get into the BIOS to see if it can be modified to try booting from the IDE port. I can't get in with DEL or F2.
2019-02-17 Tried raw copy of some existing XP disk files. Could not delete files from Linux, had to reformat. Copied XP files, tried it, got "not a bootable disk" so I have to make it bootable again somehow.