There are currently (November, 2016) a bunch of small Isotemp OCXOs available on eBay for very reasonable prices. These are in the small (about 1x1.5 inch) "Eurocase" footprint. Here are test results for one of them.
A couple of things to note:
- Startup current is over 800ma at 5V. This is more than a standard 7805 regulator fed with 13.8 volts can handle, at least without a heatsink. If you use such a regulator, try to feed it with 8V or so -- it will run much cooler.
- Steady-state current is about 175ma.
- Aging is very pronounced over the first few days following power-on, but after that it improves significantly.
This not a bad little oscillator at all (click on the image for full size):