You can order them from any supplier. You will need the OD of the upper, and lower, tubes. I fitted my '79 K with a set, secured with black zip ties, top and bottom (really had to look to see the zip ties). The '79 K's were not designed for them, but they are easy to retro-fit.
The reason I installed a pair was to prevent bug chiton/body bits from impacting the fork tubes, and subsequently cutting the fork seals as they compressed, causing them to leak. By installing gators, you can double the life of the fork seals. Cheers!
1979 CB750K (sold, 2012, but not forgotten)
1983 Kawasaki 440 LTD Belt Drive (sold, 2011)
1993 Kawasaki Voyager XII