OK. so now I know the frequencies you want, but not the purity.
I would look at a "universal switched capacitor filter" chip (not sure if ADI do them though, so google it). You can connect one up as a sine wave oscillator and the output frequency is typically 1/50 or 1/100 of a digital clock frequency. They are pretty cheap and a simple 2 pole filter will remove clock noise and leave you a nice clean sine wave.