If you don't want to spend a lot of money but want super high quality look for a transmission test set.
For $100 on flea bay you should be able to acquire a pristine specimen.
Agree. Get a used HP analog sine generator and make a nice adapter cable. HP got their start making a sine generator using a unique circuit with an incandescent lamp as the amplitude stabilization element.
An aside: I picked up one of the early (not the first) vacuum tube sine generators in pristine condition. Only the rotting leather handle betrays its age. The tubes are still the original HP branded ones. One nice thing about the old generators is that they have quite a bit of output, and it’s transformer isolated and balanced. You can drive a speaker to audible levels directly from the generator although for serious “sweeping out” you still want to use a power amp.
--Frank