I have a few Bipods myself. The last Bipod I got was also from a pawn shop for $10. It is a Chinese model, and probably for Air Soft, but I don't care, because I don't use them for everyday.
I do have a Harris Model, but it stays on my Custom Ruger 10/22 Target due to it's weight, and because I don't have Sand Bags.
I will say that the Blackhawk models at WalMart do look quite capable for the cost.