Radio codes and isolators, no leisure battery

[cootuk]

A friend has just bought a 1996 Daf 45 which has the original cassette radio. The wagon has an isolator fitted, but no leisure battery therefore no permanent live to the radio.
I assume modern replacement radios will have to have the security code entered every time, or is there a way around this?

 

[foxy]

I had an isolator on my lorry but my radio didn't need the code each time and it was a new radio as I had it fitted