A more general search like "woodwinds" would more likely be fruitful. Since the oboe is a "conventional orchestral" instrument, most places that might handle them would lump them into an inventory that covers a broader span than "just oboe."
An oboe is also a sufficiently complex instrument that - for most uses - purchase from "unknown sources" can be risky. Pawn shops in my area have quite a number of them, but virtually none with "modern" key systems.
A visit to a local retailer who stocks "band and orchestra" instruments might be a good idea, even if you intend to look for a bargain elsewhere. It will give you an idea of what a "modern" one should look like, and a chance to discuss whether/where service/repair is reasonably available.
Most such dealers in medium to large communinities - especially those who sell to high school and younger musicians - have rental programs (sometimes reasonable, sometimes not); and may have a fair stock of rental returns at reasonable(?) prices.
The caveat is the same as for most instruments (except maybe guitars, due to GAS) - those that are playable get played, those that aren't get sold.