Centro C4.2 Battery strap screws

[oldschooldriver]

My sons has a Centro C4.2 that he loves and he is not the best using a allen driver to loosen or tighten the allen screws that hold down the battery strap. In fact at the moment he has lost one of the screws and we don't have a replacement.

Is it possible to replace the battery strap screws with thumb screws like the B5m? What size screws are they? Are they Metric or Imperial?