Yes, it is available from this guy, on eBay. His user name is "Avicfix"
He has the SD cards available and a service to install them if you do not feel comfortable doing it yourself. I just ordered one from him for my 5000NEX. Most of the SD cards aer model number specific and he has them for most any of the Pioneer products.
The link to the listing for the 5000NEX is:
https://www.ebay.com/itm/PIONEER-AVIC-5000NEX-AVIC-5100NEX-SOFTWARE-REBOOT-ERROR-SCRN-FIX-REPAIR-SERVICE/302917226289?hash=item4687460f31:g:pP8AAOSw56FbaWFO
Good Luck!