I've not been there in a long while, but you might try Arlington Camera on Randol Mill Rd in Arlington. They have, for many years, been the preeminent photo shop in the entire Metro-plex area and their website, at least, shows a pretty decent selection of both Oly and Panasonic M4/3 bodies and lenses.
You could also try Fry's Electronics on Executive Drive (off LBJ freeway) in Dallas, who carries lots of Cannikon gear, but whose website shows nearly zero Olympus gear.
Olympus has never been easy to find in the in the southwestern U.S. Even back in the film days, it was nearly impossible to find new Olympus products on the shelf of any local regional camera stores. If you wanted an OM-2S or an OM-4Ti, you pretty much had to order one, sight unseen, from 47th Street Photo in NYC.
I guess Olympus just never has seen fit to do much in the way of marketing down this way.
I've been gone from Texas for about a year and a half, but when I lived in Dallas, Arlington camera was pretty much it. Kind of shocking really. One of the 5 biggest metropolitan areas in the US and thats it.