A long time ago, on a small motor I have used a pair of needle nose with the shaft sitting in the wire cutting slot on the backside of the bearing and used a good sized screwdriver to leverage the bearing up. It was a tight fit and I had to use gentle prying, but since I didn't have a clam shell puller that size, I had to improvise. I've had my shredder torn down before to the level you noted, but didn't proceed with pulling the plates any further. Problem with the shredder is the clearance is next to none, so not sure if what I did on the small motor would work or not. I looked on Amazon for small bearing pullers and I have always used clam shell as they support the bearing better than the prong types, but when you're backed into a corner, any vessel that does the job is good.
Check on Amazon for:
Search for Pinion Gear Pullers
DAYUAN 14pcs 5 ton Capacity Bearing Separator Puller Set 2" and 3" Splitters Remove Bearings Kit
Two Jaw Pilot Bearing Gear Puller, Bearing Gear Remover Tool Carbon Steel Adjustable Pump Pulley Remover Hand Tool Removal Kit Straight Type(4inch)
Prices are really good for the light work needed of them.
Hope this may help.
Cheers