There should be some good rebuilt on cheap on ebay. I buy all my compressors rebuilt on ebay.
For a compressor to be locked like that... lack of oil. Buying a compressor will also ask you to change the receiver/drier for warranty purpose. You should change yours and wih the old one out... see if you can drain the oil out and see if it is clear or blackish... if it is blackish... you really need to flush your entire AC line system.
I'd probably also change out the expansion valve at this time and all the seals involved with what you took out. Usually when you buy a compressor on ebay, they will give you compressor oil, o rings, accumulator/drier and have option to buy the expansion valve... and that would be your complete job.