It is just a regular rotating throttle barrel. I doubt you'll be find any exploded schemes with all the dimensions in it. The exploded views usually only shows the design and part numbers.

If you have the special crank-case for the RC model, you can make a throttle barrel to fit it. If you have the more common CL version you can instead put a regular carb (from an Enya 09 for instance) and use the holes from the CL spraybar to put the retaining screws through.

The engine I showed above has a simple choke above the needle (stock Webra parts), and that sort of works too but does alter the fuel ratio a lot.