there are lots of variations on white.. i always used to find that maidenhead was good..( not that i ever had white) or try online..warehouse aquatics etc
silca sand is prob your best option x
Goto LFS (loacal fish stores) or pet stores, hardware stores also sell play sand that might work. Dont go for dyed sands. AVOID DYED!!!!!!!!!!!!!! LA LA LAND HAS LOADS OF FISHES!