I bought a cheap Harbor Freight dremel last weekend and cut down the outside housing of the LED lights I got from Amazon; they are about 3/4″ deep shipped, and about 1/8″ too wide all the way around the outer perimeter. Once I’d cut and sanded down the edges, the light fit flush into the outer bezel. It’s not perfect, and not pretty, but it works. Pulling the originals out of the buckets, though, it appears the quick connect at the end of the wire is actually inside the inner fender, so in order to swap these out I’d need to (probably) pull the headlight out of its bucket to access the inner fender.
Given all the work this took, I may take Mike’s advice and just buy LED bulbs to replace the rest of the incandescents.