Very strange that you should be chasing one of these as I received a call from John Titman chasing one of those a few weeks ago.
I assume you have the drum brake H7 front wheel?
The '83 Cota 350 (last of the 349 models) and the Cota 242 model both have a similiar wheel with a spoke plate on the right hand side. I also think the last model Cota 200 may also have had the same wheel but not certain. I am not sure they are the same as the H7 wheel but Montesa tended to use common parts where ever possible. Unfortunately those wheels are also not really thick on the ground
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The H7 and Cota 350 parts book do not show a seperate part number for the spoke plate but the 242 does and it is a CFota 349/350 number (51 series) so the Trials bikes all use the same plate. The 349 was the first model with the spoke plate fitted as far as I know.
The H7 style of Montesa front wheel is very much like the late '79 early '80s Honda front wheels fitted to the XL-XR 250/500 and CR125s that had a spoke plate on one side of the wheel, 23" I think. I have never compared them side by side but it would be worth a look.
I assume you have tried Jared at North West Montesa and John at RM Montesa.
Surely someone could reproduce them. If all else fails an earlier model wheel and brake fits straight in but is not nearly as good brake.
If you send me the dimensions I will compare it to my 242. There is a 242 being wrecked at the Bone yard in the US
