Ugly, effective "on the bike" fork spring compressor from a caulking gun.
Got a set of Progressive springs with spacers for my FXR and in a fit of exasperation sliced and expanded an old caulking gun to compress the buggers. Worked well on 39mm forks and the next set of larger forks I have to fight I'll cut the ring off another gun, weld studs to the lengthwise straps and use them to secure a suitable collar, or just tack a washer to each strap then run a short piece of paracord between then under the top triple clamp.
I spread the straps to clear the top triple clamp. Caulking guns are flexible and where to slice and yank will be obvious when ya hold the caulking gun next to your forks.
U-shaped collar (make by cutting the stock circular collar with a zip disk) fits under the top triple clamp. Then ya place your spacer, fork tube cap, socket and ratchet (preferably one with a flat top for the caulking gun plunger to rest on) and squirt the cap downwards by pulling the trigger until it centers. Start threads then take it the rest of the way with the ratchet.
Tool must be held with one hand to keep it straight and I couldn't do that and take a photo at the same time, but pic gets the idea across.