Locally (Anderson, SC), our Home Depot carries a modest line of Freud router bits -- including a 7/32" plywood bit for 1/4" plywood (as well as bits for undersized 1/2" and 3/4" plywood). At 7/32" the slot will be roughly 1/64" oversized (5mm ~= 13/64"). I know Woodcraft also carries 'Plywood' bit sets as well.
I just bought my bit (actually went ahead and got all 3 bits) a week ago for 1/4" plywood panelling (to be installed in frames) and to cut slots for my drawer bottoms. I'm just using the crappy 1/4" Birch plywood (if you can call even the better pieces 'plywood' -- 'crap' is an understatement for the worst pieces!) since this is just for a shop work center/storage center to provide a permanent home for my new Powermatic 701 Mortiser.
If you use a 7/32" plywood router bit for your 5mm (or more commonly 5.2mm) plywood, let me know how it went. I could have gone the route of 5.2mm Luan plywood (of better quality), but I wasn't sure how much that extra 1/64" of slop would trouble me. Otherwise I would be interested in locating a 5.2mm plywood bit myself (for purchase), for future use.