Just bought 100 of these as I hope they fit the career cards. I only have a danish retail link, but the product code is (Esselte WW-176678)
Esselte A6 plastic pocket. (153x112 mm)
I bought some 4x5" negative holders (same size as you're recommending). They work great for career sheets, nemesis sheets, and those other oversized cards.
jh
153X112 will be a little bit big for the career cards (unless there is a difference in size between Europe and US versions of the cards...) but it won't look rediculous (5.3-inch x 4.4-inch on a 5"x4" card). I picked up some 4"x5" "polaroid sleeves" which are just renamed negative sleeve but..anywho...yay plastic.