As Greg pointed out, they’re 5/32” size. Most places now sell interchangeable bits, either individual or sets. Snap On used to sell actual clutch head screwdrivers, the 5/32” size was part number SSDC-5, then was changed to SDDC-5, now looks like they were discontinued. If you want you can search those part numbers on eBay and find some used ones, although with used you take the chance on worn tips, so examine the pictures closely.
