As Grigg pointed out a while ago, McMaster-Carr has the bits at reasonable prices.

I do not see clutch-head bolts/screws (either type) in the McMaster-Carr or Fastenal catalogs. Maybe CASO will tell us how to search for them?

Truckolet,
- Did you look at the sources at the link that Lonnie posted, above?
- Did you check out the Restoration Specialties catalog? Page 182?