I was unable to find CCC-46 rivets anywhere - searched all the usual parts/fasteners suppliers (longest they all stock now is CCC-44). ACS specifically stated they cannot obtain the -46’s. To be consistent with the rivets used in the Sonex line, I was looking for a rivet comparable to - CCC-46 Avdel ‘N’ Stainless Countersunk Flush Rivet
I found them at https://rivetsonline.com
PR46FFC - 18-8 Stainless Blind Rivet w/ Stainless Mandrel, 120 Degree Countersunk 1/8x.313-.375 Grip