For the benefit of others later finding this thread, the Kent Moore tool is J-37767 for that 14-point lock nut, variously called a Brake Booster Push Rod Wrench, Brake Booster Adjustment Tool, or Brake Booster Adjuster. Correct? Some online tool places are selling those for ridiculously high prices, with legitimate private sellers more in the $30-$50 range on eBay.

Being cheap, I'm trying to think of ways I might make a home made wrench that wouldn't risk damaging the nut or shaft, yet provide a really good grip. That soft aluminum clamp block in that old Brickboard posting is one idea. As was also mentioned back then, slip joint or other pliers with a curved section of coarse teeth that closely match would be worth a try as long as you don't slip or strip the nut. Now that I've seen what they look like, I'd probably try to fashion something like that Kent Moore tool out of flat bar, drilling an undersized hole and using a Dremmel diamond bit to carve for the 14 teeth, possibly with a very slight taper for a tighter press fit, maybe even try hardening it afterwards.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now