Fortunately I had one on the spare Falco that I nicked, but needed to get a replacement eventually.
I had a look through a few possibilities, but getting stuff posted to the arse end of the globe makes most options uneconomical.
In Jaycar (electronics store) I stumbled upon this for around $50 and bought it on impulse.

Solid state relay, 3-32V input and good for 100A. Noticed later that the max trigger current is 28mA and the current at the solenoid is about 1.7A. Quick calc and all I need is a 500 Ohm 0.5W resister, which I just happened to have laying around.
Lashed it up rough on the spare bike and pressed the go button and it works.
I’m going to put it on the daily ride and see how it works, I'll do some pics of the install. No moving parts and no contacts to arc means it should be better than the original.
Just wanted to share.