Hola, you two. I been popping in and out checking your wonderful adventure which was a bit more than you had hoped for these last few days. First and foremost I am very glad to know wife is on the road to recovery.
OK, that said, I assume you are looking at new bike, lots of good used one go check out the flea market here. I would say it would be best for you to get back across the border if your not too far in. Remember you'll still need to purchase said bike and get the title in your name for border crossing down the line. somehow get her DRZ hauled out or forfeit the import fee of 300 or 400 USD, but you know that.
There are numerous good used vehicles too to consider, the only hold back I see is the height (yours), you'll more than likely need to have the seat shaved an inch no matter what, unless you get a cruiser
I understand your frustration at the insurance issue, I have had Geico for years now and I assure they are great provided your in Canada and USA. No one and I mean one I know covers motorcycles for full coverage down there.... liability only! you can get full coverage on cars.
heres a link for you to review: http://www.bajabound.com/info/policies/motorcycle.php
Wish I could help out but all I have is a 2006 Triumph Tiger I'm willing to part with and I am a long ways away.
Just come back over the border so you can find what you need and get the paperwork in your name.
BTW there are dealers in SA
I have enjoyed following along on your epic ride and this is a setback, frustrating as it is, what's important is she's OK.