Many thanks for the responses chaps. Much appreciated.
The bolts are the bedding bolts for a CZ rimfire.
Replacement screws (i.e. same ones) can be found in abundance but isn't what I'm looking for. As mentioned in my earlier post, what I'm chasing is to upgrade the bolts, replacing the slotted head with either SCH or Torx.
Agreed, slotted heads do not get chewed up if treated correctly but 1. you don't always have the luxury of guaranteeing that previous owners have used the correct tools (it's secondhand) and 2. I've given up trying to find a 10mm wide screwdriver bit that fits in to a 1/4 drive torque wrench.
Iain