Thanks for clearing that up! As
@Tim Hall mentions above, you should be able to get perforated stainless or alu alloy strip quite readily to fabricate your own supports, but really, any racks offered for sale on
ebay ought to include these. The fitting varies with different racks, though - two of my bikes have Tortec expedition racks, which come with
these fittings, which work well with that rack design, but
these are also available, which might be easier to adapt for other racks.