I don't know nothin' bout Rodeos, but....
have you tried to access it from inside the vehicle (is there a release handle there?).... is there a panel on the inside that you can remove to get to the lock?

You can go to http://www.myisuzuparts.com/ and punch in your vehicle, then punch in "parts catalog"... underneath that "sheet metal, glass" then to the right box "back door and hinge"

Also underneath "parts catalog"... "interior components" then right box "lock cylinder set".... choose your "vehicle options" and "submit".

That might give you some ideas.... otherwise call your Isuzu dealer (if you can find one <img src="/forums/images/graemlins/lol.gif" alt="" /> ) and ask to speak to the mechanic most knowledgeable on Isuzu's.

HTH
Van <img src="/forums/images/graemlins/patriot.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" />