The below one is a whole sale distributor.
They do sell Mystic White II Swimming Pool Filter Sand - 50lb Bag
https://www.amazon.com/Mystic-White-Swimming-Pool-Filter/dp/B00VSNUO6S
Please reach them to buy multiple bags.
SCP Distributors,
7270 Park Cir Dr,
Hanover, MD 21076
(410) 712-9440...