AheadSet Retainer Bearing Headset Bearings (100092296) at CambriaBike.com

not that these are necessarily what you want, but... the point is they are, in general, not expensive. so i'd go to the LBS and pick up a pair if you are in doubt. they may even have on hand what you need. i'd take the bearings with me to the LBS to show them what's called for.