Thank you to everyone that responded. Seems open cage ones in that size are fairly expensive. For now I'm just gonna order some cheap ones and hopefully pop the covers off.
Even if the cheap ones turn out to be crap, I need them to verify the encoders work.
A pack of 100 seems to only cost a few more bucks than 10 or 20. Seems I have to find more uses for this size.
You shouldnt need to pop off the covers. In fact, you would might even end up damaging the bearing, while trying to do so.
(smaller bearings are more likely to suffer from stress related damages, due to thinner metal wall-thickness)
Electronics cleaner will easily flow past the typical bearing coverings, because they are rarely ever sealed "fluid-tight".
3-in-one oil, will also easily work its way past the bearing covers, in a very short amount of time (no need to soak overnight).
You also really do not want to run your bearings "open-air", because dust and crud will eventually get inside of them.. and will start
to cause uneven friction and potential damages to the inner Races... and the bearing holders.
If you put most of these sealed bearings into water... the water would easily flood into them, and start rusting them up internally.
Now... They probably make bearings that are completely fluid sealed.. but Im certain that they would be MUCH more expensive,
and it would Note it on their description. They would likely need to have a special sealant, maybe similar to silicone, applied to the
Side-Caps.. and if you broke these seals, you would permanently damage their effective seal.. unless re-sealed with the same sealant.