Who can re-flash ECM computers-Need to Replace it

Well, those dang Mice got into our cabin garage last spring, and chewed through wiring on my 2006 Outlander 800, resulting in shorting out the computer ECM, when I ran it again (Dealer diagnosed) they are crazy expensive new ($1,049.00+). I found a few used ones for less than half that. They are one year newer & from different engine CC sizes. My dealer is a small one, & said they have not done a complete re-flash, & wasn’t sure if a used one would work. I see some on craigslist and eBay. (anyone have one for sale?) Any suggestions who to call or where to go??? thanks!