First
you have to determine what thread size they are.
They look like either 12/24 or 1/4-20 carriage bolts. (pressed or fused in place)
The 1/4-20 carriage bolts are readily available in most hardware stores (at least here)
The 12/24 carriage bolts are virtually extinct but 12/24 machine screws are available from various hardware suppliers.
