I have not followed this thread in detail so may be off the mark. If do disregard it.

   Bristle is still in business and is on the web.  They sell full sets of L wrenches. The number of fins varies with size, larger ones are 6 fins, smaller ones have 4 fins. Spin-Tight style wrenches are made by exelite. The set comes with an extension shaft.  Will reach set screws where the L wrenches won't go. You really need both sets.   If the heads are messed up you may be able to get them out with a EZout. Can be delicate for small sizes. May take a milling machine to be steady enough. If worst comes to worst drill out the screws and rethread for a larger size.   I would try the ezout first to see if the screws can be removed without damaging the shafts.

FWIW "grub screw" is British English for a set screw.