Was in the hydraulic business for 35 years and a lot of spanner nuts used in hydraulics. Have made many special spanner wrenches over the years using allen wrenches for the pins.
Depending upon the tools at your disposal, you can braze the pins to a C shaped piece of flat stock, say 1/8"x1/2 or 3/4" and braze that to a handle. The size can be adjusted by squeezing the C in a vise to close, etc.
Another method that would work well for the type of nut you have is to select the allen wrench that fits your hole size and simply drill two properly spaced holes (to fit your nut) through a short piece of 1/4" thick flat steel. Drill holes a few thousandths of an inch smaller than the allen wrench and press a couple of short pieces of the allen wrench into the handle.
Regards,
hm