Cheers for the update.
The way you describe your findings confirms your carbs are from a CSR. They were set to meet USA emission regulations and also to be ‘Tamper’ proof. Tamper proof being that the carbs could NOT be adjusted as there was a plug over the mixture screw and the needle could not be adjusted. However the plugs can be removed and adjustable needles can be fitted. Alternatively the needle can be raised by inserting small washers below the circlip.
As far as refurb kits are concerned my first port of call would be
If they can’t help then so far it’s the dreaded fleabay