I have a heavily modded Heathkit audio generator, which I'd be happy to
sell.

I don't remember the model number. About 35 years ago, "Audio Amateur"
published an article on modifying this generator for ultra-low distortion.
The "catch" is that when you change frequency, you have to wait a second or
two for the generator to settle.

I'd sell it for the original price of the kit. If you're interested, please
get in touch with me.