That increases complications.
I believe there are two flash memory dumps you need from the radio, to calculate the code. Apparently it cannot simply be calculated from the serial number. But if you can get the flash dumps, a website like digital Kaos or MHHAuto will have someone able to help with code calculator. It might cost you some Euro, but should not be great.
It’s quite possible that without technical experience yourself, the cost by a specialist to read EEPROM (your flash dumps) before calculation, may be greater than the cost of buying a newer radio with superior features.