Use this to add a 5 pin DIN connector to your Rega tonearm and use any aftermarket 5pin DIN to RCA cables. 

I got a connector plug from Aliexpress and soldered my RB110 tonearm wires to the plug using this pinout guide. The adapter ring goes over the connector plug and is secured with the original grub screw inside the tonearm base.

You may want to print a couple of these with different scale factors (e.g. 99%, 100%, 101%)