I spent years bugging the good folks at Paragon to make these, and thanks to someone with more pull (thanks, Drew!) also bugging them, they’re finally here (after a first-round hiccup). Here’s a picture. They will take Rockshox or DT 15mm axles (no Fox), they’re beefy as heck, I like them. Extra $50 upcharge, but you get an axle (RS or DT, your choice) out of it as part of the deal.
With that out of the way; here’s a brief rant: You do not need a through axle on a rigid fork. If you want this setup for convenience when swapping suspension/rigid forks on your bike, great. But there is really no performance benefit unless you’re 300 pounds or riding a tandem or something. Suspension forks need this kind of axle because they are inherently not very stiff structures (2 pistons joined only by the crown and the arch) and adding a very stiff axle at the bottom of the fork is enormously helpful. Rigid forks do not suffer from torsional or lateral stiffness problems, so a big axle is pretty meaningless.
With that said, I’m happy to build you a fork with these dropouts either way. The 15mm axle isn’t going to hurt anything, so worst case scenario, you’re still good and you spent $50 on a big axle.