Have to agree with Steen here. It’s probably not worth putting too much $$$ into a blown clone. ;)
Buying parts is typically more expensive than buying complete units, so starting with a decent used motor and a “freshening” will likely cost less in the end.
You can send your PRD into any builder for examination and repair estimate, and right out of the gate you’re hit with the expense of shipping.
You could try Comet or LAD or P1 or Woltjer or any of the many engine builders.