http://www.hsbaseballweb.com/showcase/showcase_table.htm
The link above will take you to Showcase promoters listed here on the site. I'd suggest you stay with proven showcasers...They tend to hold events in more densely populated areas, or within a few hours drive of "hotbeds", like Texas, Calif, Fla., & Georgia. You may need to travel to Kansas for a "regional" showcase.
Perfect Game is by far the most extensive & talked about here frequently. The Fords are terrific people & Jerry posts on this site quite a bit. Give him a call, you'll be glad!
Personally, I saw no need to try them all (or any,) other than PG). The Baylor Underclass, &/or Top Prospect, along with Sunshine South Houston), are terrific. And, Okla Coaches are seen at PG's WWBA Tournaments in Marietta & Florida every summer & fall.
Team One has "teamed up" with Baseball Factory. Some posters may be able to contribute opinions....mostly on the East coast & Fla.
There are big differences in all these operations & I'd suggest you do your homework.
As for a specific "Oklahoman" showcase, I don't know of any one. However, you may want to check with recruiters at OSU, OU, **** Roberts, & a couple of the top Juco programs. Often the schools will "co-op" a smaller showcase. Your HS coach or some of the top select programs/ facilities (like All-Star in Tulsa, or Okla. Baseball) may have some input here, too.
Good luck & keep asking questions!!
ps. This hsbaseball web classic is a must read!
http://www.hsbaseballweb.com/showcase/bubba.htm