Where to get a case of silicone for tank.

[zum14]

Hey, so im trying to track down a case of silicone. Ive read through a lot of the great debates on silicone. Im thinking maybe GE 1200 black. I have a tank im going to do and one I need to re seal so I figured a case. It seems tough to track down in PG. Maybe im calling the wrong places. Anyone know where to get some, or in Van too works.Thanks.