I did the same thing this guy did with my 2016 22RR:
I ordered
this carrier on Amazon (same one he references as the model he used, but a lot cheaper than from etrailer.com), then went to the local big-box hardware store and got the following hardware:
Hillman 3/8-in x 4-in Zinc-Plated Coarse Thread Hex Bolt (4)
Hillman 3/8-in x 16 Zinc-plated Steel Nylon Insert Nut (4)
Hillman 3/8-in I.D. x 1/2-in O.D. x 1-in Long Seamless Steel Spacers (4)
Hillman 3/8-in Zinc-Plated Standard (SAE) Flat Washer (16)
I put the mount plate for the carrier upside down on the center of the bumper (there's a tab that locates it against the top of the fender: it perfectly catches the bottom of the bumper to help locate the plate), marked the top holes, then measured about an inch from the bottom of the bumper to a point roughly in line with the factory holes in the mount plate. Because its upside down (which is required to allow the carrier to fully pivot down to the ground), the factory holes for use with a box bumper are now in space: so I drilled two new 3/8" holes in the plate for the lower mount points. I replaced it on the trailer, held it in place with a c-clamp, then drilled through the bumper. To mount, I put the bolts with washers on the outside face, inside face, the 1" spacers, another washer and finally put a washer inside the bumper and secured it with the nylock nuts. Added an inexpensive spare tire cover (after assembling the carrier bar using red loctite on the two nuts that hold the tire-mount point in place). Pull the pin, and the assembly drops to the ground and the door is fully accessible.
Time will tell how durable the carrier will turn out to be, but evidently the guy who's video I linked to has been using the setup for a few years. (Sorry: for whatever reason, the forums' software uploads pics sideways every time!)