Andrew,
I had the same problem a while ago, I too remembered the IBM keyboards that came with IBM Systems.
After a lot of searching I came across 'The Keyboard Company' who supply some really good solid keyboards.
And they are a UK company in Gloucestershire, but not UK made keyboards. They know a lot about what they sell and the options.
You might find the prices a (mild) shock if you would normally buy the ones available on the High Street. But for me they are worth every penny.
And they have selection. They even have an up-to-date version of the original IBM keyboard.
I bought, on their recommendation, a Filco FILCKF15 which is as near to the IBM in use as I can recall. You can specify the key tops you want.
You probably know a lot more about keyboards than me, when I ordered the second one, for my CAD system (Inventor) I accidentally ordered with blank key tops!, but the quickly supplied me with the UK tops, but an expensive mistake by me. I should have known better and read the specs more carefully. The first came with a uk set any any way.
Delivery to me in Mansfield is usually overnight, even if I order on Friday afternoon.
Hope this helps
contact details
The Keyboard Company
Unit 8 Canal Ironworks
Hope Mills, London Road
Stroud
Gloucestershire
GL5 2SH
United Kingdom
http://www.keyboardco.comTel: 01453 884938
Jerry