Is there an existing NIP-47 server implementation that calls a NIP-46 bunker to sign the zap receipt?

And is there an existing NIP-46 implementation that would only sign zap receipts, and refuse to sign any other kind of event?

The combination of the two would let users receive zaps self-custodialy by running the NIP-47 server on a cheap VPS without exposing their npriv, while running the bunker at home (for example behind TOR).