I currently have a good idea for a gimmick that would be built into a card box. Obviously, this type of thing is nearly impossible to mass construct on one's own. Who can I contact about creating the gimmick? Thanks so much.

http://www.elmwoodmagic.com
http://www.murphysmagic.com

Both companies frequently buy the rights to manufacture effects, and are wonderful to work with. Info on contacting them is at their sites. You'll want to contact Paul Richards at Elmwood, and Tim Trono at Murphy's.