Saltwater fishing supply will be the likely place if you are looking for Dacron line used for fishing. Kite stores are another source, and the more likely place to find it on the internet. For the same pound test, it will be about half the diameter of mason's line.

Dacron line is not cordage. It is string, much the same as a heavy floss. There is some care as to how to tie it off, as its abrasive qualities can be a concern in certain bights and binds.

There ought to be some place around Houston that carries dacron fishing line.