Easy to make.
Short lenghts of 1" box tube with slot cut whole length in centre on one side.
8mm bolt or threaded rod cut to length and slot cut in one end.
Penny washer with edge welded into the slot on bolt / thread rod.
File hole in penny washer to take the square bar out of a normal household lock handle set.
Assmeble with wing nut and job done.
This is what I did using stuff that was lying a round and it doesn't take long to make them.
Only problem is it was ages ago and I cann't find them now so will have to spend 1/2 hr making some more but still better than paying nearly £25 a set.