For the UK, I found
CIMPLE Solutions Pro Ltd for K701 and K601 pads. Haven't ordered anything yet, and I wonder if they actually stock, or just order from the UK's AKG distributor. Never contacted the AKG UK distributor so I don't know if that would be a better solution service or price wise. Anyway, you have to search via part numbers on cimplespares.com, which I got from the AKG technical manuals on their site. I've also added the current prices on cimplespares.com:
K601 pad / cushion: part number 2458M1101 - £8.60 excluding VAT
K701 pad / cushion: part number 2458M1201 - £10.06 excluding VAT
Foam ring for both: part number 2458Z5801 - £0.28 excluding VAT
The foam rings are the same for both the K601 and K701. All of these are for a
single pad and foam ring as far as I can tell (considering they are named singular, usually sold singular, and listed singular in the AKG technical documents (quantity 2 is specified per headphone)).
Still not sure whether to get K601 pads of K701 pads. My K601 pads aren't broken, so really I should just wash them, and in regards to that I guess I should try out the K701 pads. I noticed that the K601 cups don't pivot laterally much; does this cause any long term bending of the two struts that link the cups (when using the angled K701 pads)? I'd imagine not as they seem to have a good amount of give, and aren't held too solidly in the clasps that attach to the head band, but I just wondered if anyone noticed any long term problems, or a reduction in clamping force when the K601 pads are put back on.