If I were to guess the weight (sorry, no scale), I'd be confident in saying that they're in excess of 1,000 grains.
You can buy them from stores that sell bowfishing shaft materials, or do what I do, and buy fiberglass poles of the same (5/16") diameter and cut em to length.
For some reason, some of the poles of been getting recently are none too straight. But simple culling gets rid of that problem. If they're straight when you get em, they're like carbon or aluminum: they stay that way...
And about the ones from Foxfire...I think they only go up to a #47 spine...