The c-spec, a-spec, z-spec are I believe MilSpec (mfgr) version of the camloc, airloc, dzus fasteners and are usually marketed as "compatible" to the latter. I think Skybolt(?) also has a version called c-loc, z-loc, etc. There are some other quick-turn fasteners out there but they're more specialized then those on your current list. The important issue is not all fasteners perform equally given the purpose used.
Check link below. If the specific page doesn't offer what you need, call them direct and explain. But keep in mind some cowling is considered structure depending on how the cowling interfaces to airframe which makes substituting quick turn fasteners a bit more of a challenge and may fall under 43 Appx A(a)(viii) Elements of an airframe including spars, ribs, fittings, shock absorbers, bracing, cowling, fairings, and balance weights.
Really???
