I don't understand why this is so hard....
Contact a modelling agency in the city--there's 5 of them in Tulsa. Explain what you want to do, and ask for the rates of the models. Emphasise that this will be NON-sexual in nature, and offer the option of model posing while partially clothed.
If you are a student, post a classified ad on the job board at your local college or university, and offer a nominal fee.
If that does not work, place a classified ad in the news paper or on Craigslist.
It might be an expense, but if you contact several fellow artists to join in the endeavour, the costs can be shared.
The advantages are that you can write off the costs as a tax deduction IF its a learning tool for developing professional skills.
Failing that, ask family members to pose, dressed of course. The more serious you are about it, the more likely you will find someone that will understand your needs.
"We all grow older, we do not necessarily have to grow up"--Archie Goodwin