FYI, in case anyone else has had to replace broken (front) floor mat retainers on their EX, the correct part is called a "BRACKET-CARPET, FRONT" and is part number 74985-EH10B.
http://www.nissaninfinitiparts.com/oe-i ... 74985eh10a
Takes a minute to pull out the old one and pop in the new ones. No more sliding floor mats!