The two threaded rods on the front of the front rack are an ideal place to hang the DC-DC converter. So, I doodled a converter up in Sketchup, and then designed two angle-brackets-with-box-tubes to slide down over the threaded rod and mount the converter:
I then built it. These are two 1.25x1.25 1/8" angle brackets, welded to a 0.5" 1/16" box tube, all 8 inches long:
After mounting and drilling the pieces, I decided 8" was too long, so I cut them back to 7" - this shows the shorter length. 8" would have interfered with the top of the front rack:
And here is the DC-DC converter in its final home. The only 1/4 20 bolts I could find were some grungy old carriage bolts - all the hardware stores are, of course, closed on Sunday night. I'll pick up some better bolts this week:
Note that both components which require cooling (the DMOC445 and the DC-DC converter) are directly behind the original front grill, for high airflow while moving.