I have bought semolina flour on several occasions at Whole Foods in Dallas, in the bulk bins. I believe there is a Whole Foods store in Arlington, which may be closer to where you live. Whole Foods also generally carries the full range of products put out under the brand Bob's Red Mill. Semolina is one of the products. There is also a store locator at bobsredmill.com, if that will help.
I used the semolina for pasta but I assume that it would work for Randy's recipe.