Hi again Uwloian, Yes, any Home Depot, Lowes, and even hardware stores carry sand. Playbox sand is very good because it usually has been washed (less dust).
The best coated lead shot that I know of can be purchased at a local dive shop. Coated shot is often used in ballast bags. It is simply a wax coating applied over the actual lead shot in order to avoid direct skin contact. Lead is nasty stuff.
Also, you may want to consider circumventing your dealer completely and contacting Paradigm directly. Ask to speak with one of the design engineers or a tech consultant regarding usage of stand fillers. After purchasing my speakers, I contacted Energy directly and spoke with an extremely insightful engineer. Not only did he suggest what substance to use, but he also suggested how much to actually fill the stands.
I used tall kitchen garbage bags to act as a "bladder".
Best of luck, Ed.