I'd go to a wrecker and look at a s/h Bosch off an EA-ED Falcon. Mine looks about the same size as the Mini's one, but brackets may need a bit of a mod.
Wiring is similar: +, - and indicator light.
I think the stock one is 45A, taxi pack 65A?
Look at others while you are there- most small sized Jap ones could be made to work, mounting is probably the main hassle.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.
