Hi Jason,
I would try calling Mark Butterworth at
http://butterworthclocks.com and also Steve at
https://timesavers.comI think you can purchase the center wheel from them but not sure if it comes with the compression spring. They might sell the spring separately so might be worth the time to give them a call. Other than that pulling it off of an old movement would be the only thing I can think of.
Hope this helps. Good luck Jason, Dan