You can also google Oklahoma Property Management. It will pull up a list of local companies that specialize in rental property. They may be able to direct you.
Keller Williams Realty
As long as the landlord is an approved Section 8 vendor w/ the particular distributor of your voucher, any home can be submitted for Section 8 rent.
Check The Oklahoman for rentals and drive the neighborhoods you like and call off the For Rent signs and just ask the landlord if they accept the voucher.
Oklahoma does not have a true "for lease" market, which causes the previous mentioned locators the preferred option for renters.
Hope this helps,
Josh Barnett, Realtor