The large bearing on the front is an NSK 60/22DU. The small bearing at the rear is an NSK 6000DU. Honda lists the small bearing as 31113-MN5-005 the Honda parts catalogs I have don't show the large end bearing. Normally if there's a problem with a bearing in the alternator it's the small one. You should be able to call a bearing supply shop and cross reference the NSK bearing numbers usually these type bearings are a pretty common size.
Try a bearing dealer. Went to local bearing dealer here in NH when planning to replace my 1500's front/rear wheel bearings. All were available except one for rear wheel.Saved quite a bit of $ over OEM. My 2 cents......Old Tom