I hope this is a help to other parents of children with sensory integration issues out there... Weighted vests are pretty pricey, and limiting, so I've found a good alternative.
I have added weighted pockets to a ready-made vest.
The pockets are made of a strong cotton twill, and since they are meant to total a percentage of the child's body weight, small beanbags work well.
So that the pockets don't have to remain attached to the same garment, they are removeable. They have two large buttonholes on top, so the buttons can be sewn to whichever garment is suitable for the child's size and the season.
I will sell the pockets and appropriate buttons, or directions to make them, if desired.
Here is a picture of the beanbags...
Here is my son's vest with pockets sewn in (but they can be buttoned on instead.)