Does anyone know if a replacment bearing is available that dont need the black plastic top hat spacer? As fitted as standard to Shimano Ht 2 bottom brackets.

Not sure going without the spacer (assuming correct internal dia on the bearing) is a good idea. More likely to cause damage to the axle of the crankset if bearing goes.
(Sorry i know i havent helped answer your Q)

these ones don’t but I think bigyinn has a point

(on the other hand, I suppose the bearings will be bigger so may not be so poor in 1st place)

how long after they’re knackered are you going to leave them on the bike, or are you not going to fit them with any grease?

There is a good reason why all crank manufacturers use a nylon bush, the only people who dont – dont make cranks…. says something dowesnt it about the thought gone into them