RV,
Envirotex is something I have purchased at Menard's, a midwest home improvement store. I have never seen it at Lowes or Home Depot.
It probably is overkill for a Ball Python since they don't have excessive moisture requirments.
If I were converting a dresser into a BP cage I would first line the floor with 1/4" expanded PVC. A frame or subfloor may be necessary to support it. PVCX will allow for the use of "belly heat". It will also make for an easy to clean and fairly durable floor.
Depending on the structure of the dresser I'd probably line it with a thin laminated plywood of some sort, almost certainly maple, birch, or oak.
The walls of the cage would then either be painted with an oil-based paint or stained and then coated with an oil-based polyurethane. Both would be cheaper than Envirotex but would take a lot longer to offgas completely.
Another option is to line it with styrene insulation and do fake rock-work similar to Oogieboogie. See one of this posts for a link if you have not already.