I don't know where in Ok you are but here are a couple of shows coming up. There is an AKC show in Enid Oct. 15th and then there's one in Shawnee and I think one in Lawton after that and if you are anywhere close to Tulsa there is a Chihuahua Club of Oklahoma show in Tulsa on November 3rd.
The season is just beginning to pick back up here, it pretty well ends for a few months during the worst of the summer heat.
The easiest place to find information is at www.akc.org, click on events then click on conformation and put Oklahoma in the state box and it will bring up all the Oklahoma shows for the year.