Boyer Bransden don't make a specific kit for the RD. They do however make Inductive Discharge units for £22 each. You will need two and they use the points to trigger a low voltage signal to fire the plugs. I have not used them, nor do I know of anyone who uses them so I cannot comment on how good they are. If you do, let me know please! Suffice to say the idea sounds good, point life should be longer, sparks fatter but remember you will still have to adjust the points eventually due to mechanical wear.
Piranha are now made by Newtronics. They consist of a transistorised unit to fire the plugs. The cost is around £60 (exc VAT) +postage. Overseas customers obviously don't need to pay the VAT. The points are replaced by optical triggers, that once set will probably never need resetting (no moving parts to wear out). These trigger the transistor switches in the 'Black Box' to make big fat sparks on the plug. I have one on my RD400C and can vouch for it's worth. Starting is easier, the engine revs out more easily, fuel economy is not changed such that I would notice, and I haven't had to retime the bike for 5 years so far (since I fitted it) other than after a crank rebuild!
Where to get them ?
Newtronic Systems What to ask for: If you have a Mitsibushi alternator (generally US models) - YAM2A European model alternators (Hitachi) - YAM2