The Leupold custom shop can do some reticle refits, depending on the scope model, but you're limited to scopes and reticles offered by Leupold. The custom shop is currently closed due to last year's dumpster fire.
A truly custom reticle would likely cost an absolute butt-ton of money. David Tubb has a line of his own custom reticles in Leupold Mark V scopes, so you might ask there about how to go about getting such work done.