Fortunately the Lucas K2F magneto isn't rare, new points and bearings are readily available if that's all that's needed beyond stripping out and cleaning the cam ring and the points already in there. At least they are over here, I think I found a few US-based magneto repair shops on the internet too.
Your options are repair, replace or go for some electronic gubbins.
I'd go with the first if you have the $$$, you might have to go full rebuild on it which would also mean a rewind for the armature, new condenser and may be slip ring as well as bearings, points and re-magnetising. Also check for wear on the cam ring itself - assuming it cleans up OK - uneven wear can cause variation in ignition timing between the two cylinders, though this can usually be put right.
If you replace it with another magneto (would that you could still just get a service exchange unit from your nearest local Lucas depot!) make sure you get one with the right rotation, check, but I THINK the RE twin magnetos spin clockwise at the drive end (anti-clockwise at the points). Other British twins' magnetos spin anti-clockwise at the drive end, same as the Bullet in its magneto-fired days.
Should you be tempted by electronic there are still more options, including a replacement drive housing with a Boyer or Pazon ignition (to name but two), or even a new electronic magneto from BT-H, basically CDI tech but still independent of the rest of the electrical system. I'm using the single cylinder version on a couple of my Bullets and they seem pretty good. But that's a way bigger buck option than getting your existing magneto professionally rebuilt, I suspect!
https://www.bt-h.biz/K2F--Lucas-Replica-Flange-MagnetoA.