I know someone that used to work in the OKC area for an FAA contractor. I think they worked on setting up flights to check out navaids at various airports. It wasn't really dispatching, though. I can try and get more information on it if you want. I think the FAA may have a few dispatchers other than the PDI's on staff, but I'm not sure what they do exactly. JPATS (the "Con Air" prisoner transportation planes operated by the feds) does have dispatchers, but I am not sure if their office is in OKC or not.
As far as dispatch offices in Oklahoma, Omni Air International is headquartered there, but in TUL and not OKC. While I don't think they have stellar pay, it is good long haul international dispatching experience. I don't know how often they hire but they might be worth checking out. Other than that the closest dispatch offices to OKC would be in Dallas, which has Envoy, Southwest, and AA, or in Little Rock, which has Air Transport International, a cargo/charter airline.