What @rsingler said. I use DGX trim weight pockets. I have 4 of them, just so I can put 2 on each tank strap, if necessary. They will hold 4# each.
They are very secure and only $10 each. 2 more would probably also work well on the waist belt with a couple of belt keeper things behind them to keep them from moving around.
DGX Trim Weight Pocket (each)
They are very secure and only $10 each. 2 more would probably also work well on the waist belt with a couple of belt keeper things behind them to keep them from moving around.
DGX Trim Weight Pocket (each)