Why not make your own? I did, with help, though mine was overcomplicated and I wouldn't do it that way again.
Requires fab and weld skills, but most of us know someone who can weld if you can't yourself, and the fab part would be easy. Summit sells Moroso weld-in fill bungs with caps, both out of aluminum and steel. Likewise, they sell steel and aluminum AN weld bungs from several manufacturers, as well as lengths of steel and aluminum tubing in lots of diameters.
My thinking is to decide on a material- if I was doing it again myself it would be steel since I don't have the skills or equipment to weld aluminum, but I'm handy with a MIG and I own a wire feed welder. Steel it would be.
Decide how tall, cut a length of tube and some circles out of flat sheet. Weld together. Decide where the hose bungs should go, drill holes and weld bungs in. Cut hole for, then weld fill cap bung to top. Lots of ways to attach to the Explorer accessory drive mount- weld on some tabs, make a clamp, etc.
A steel one probably wouldn't look as pretty as a professionally machined and welded aluminum one, but one could fab it such that it fits perfectly.