I haven't done this job myself, but a local who has a dead heater on his 2013 RAV4 EV asked me to look into this about a month agao, and it appears that you can obtain a Leaf heater from an early Leaf (say, from eBay), get a harness fragment from the Leaf as well, splice the HV harness from the RAV4 to the Leaf's harness, then replace the fuse inside the DC-DC (a fairly easy job, not like changing the fuses in the OBC!), and DIY this for about $500 and an afternoon of work. Again, I haven't done it, but it looks straightforward. Is there a thread on this forum about DIY the heater repair?