Sadly I do not know of any stores in the specific area, but a large variety of garden stores sell sage plants as well as white sage that you can dry yourself if desired.
If you would prefer dried plants you can order them online, the SoM store stocks some herbs, I am unsure about whether this particular store sells sage but there are many others online that can ship to your area. The only issue is that a large number of countries do not ship plant material across countries, so you would have to find a store based in the US.
There are many stores in texas that sell sage. Typically metaphysical shops are not listed for easy access on the internet. Mostly you have to find other ways to find these locations. What part of texas are you in and I can help
I honestly but most of my seeds for my own herbs online. Because I am a huge fan of Blue Sage it's very difficult to find and there is more then one species then I grow it in my house during the months it's not compatible to be outside. But I live where there is a harsh winter. For use I also purchase 90% of my products on line aefer much research. Research of the product line and products is key.