All you really need is a decent opamp, three resistors, three caps. Make one of the resistors adjustable, otherwise all components same value. It's called a phase shifted oscillator and it has very good, very low distortion. The gain of the amplifier is set by two additional resistors.
That's one way. Another is a simple 555 square wave oscillator, then use an R/C filter to, "Trim," the harmonics (edges,)which will have produce bit of distortion but you can control that by setting the R/C corner frequency, then make up for lost gain with a second stage of gain to get back your amplitude. The start though is a good accurate square wave, symmetrical, because the R/C filter will not, can not fix asymmetry.
If you want I can draw you the schematics & values, send it over.
