I purchased new bearings from Mcmaster Carr (
http://www.mcmaster.com). The front bearing replacement is a standard R6 bearing, and leaving the shielding in place won't hurt.
Part numbers at Mcmaster are
60355K35 Steel Ball BEARING--ABEC-1, Dbl Sealed Bearing No. R6 For 3/8"SHAFT DIA,7/8"OD
5972K144 Steel Ball Bearing, Open Bearing No. 6902 For 15MM Shaft Dia, 28MM Od
Brad