Forget servos: they're just not strong enough for anything beyond the lightest of point-n-shoot still cameras.
I've seen some low-end units from China on ebay for about $100-150 that claim to be strong enough to handle a few pounds of camera. They probably wouldn't stand up to heavy use for very long, but would probably do for tinkering.
You might also check with any security/alarm dealers in your area, and ask if they've got anything used from systems that have been retired or upgraded. If they've made their profit on them, they might be willing them at scrap-like prices.
Ran