A search on "rivet set" will turn up several suppliers of 0.401 shank sets to form round heads. The beauty of the .401 shank is that it is the standard for air hammers, whether they are cheap from Princess Auto or the more expensive ones used for aircraft riveting with "teasing" soft start triggers. For the larger steel rivets used on the carrier (and on CMP frames) you may need to have the rivet shank a tosty red, or better, before trying to for the head. Either heat or a pretty sturdy rivet gun will be needed for the larger steel rivets. Assuming that you want round heads on both ends of the rivet, you may want a bucking bar with a matching dished space for the preformed rivet head. Also, let the rivet set air cool rather than water (or oil) quenching it to avoid changing its metalurgical properties (brittle fractures on impact tools can fly dangerously).
Many of the suppliers are mainly aimed at aircraft building, some do internet commerce.
See:
http://www.rivetsinstock.com
http://www.bylerrivet.com/
http://www.hansonrivet.com/
http://www.rivet.com/
http://www.fastenermart.com