I have a problem with some old circa 1980's machines that I service because they use purpose built AT keyboards with a five pin din plug. The key switches start to fail so I have to solder in new switches, but some of the boards are in a poor state and I cannot aways fix them and I'm running out of switches.

Using a new PS2 keyboard with to 5 pin adaptor doesn't work as the keys don't match, but when I test an old AT board in a new PC using the opposite adaptor the keys match.

Does anyone know where I can obtain a few old style AT keyboards?

Theres a couple of them on ebay.

Fleabay is probably your only hope. But I'm sure I've seen a company online that refurbishes old IBM M keyboards. But I think they modernised them too which is probably no use to you.

Here is one

ClickyKeyboards

They do all seem to be in the US.

Here is a new one

Techinfo

I think I have an old AT keyboard in the attick with a 5 pin DIN plug.

You're welcome to it for the cost of postage if you want