Simtec look like they're nearly ready to start shipping USB podules and ISA
cards.  Ok so this is more biased towards acorn archs, but an ISA USB card
has got to be different, not sure if it'll just be for the riscstation
though.

http://www.simtec.co.uk/products/riscos/usb11pod/

Time to check if we support the phillips ISP1161A controller...

Chris