I have seen pictures of the short T4 4 watt fluorescent bulbs, but I have never seen them listed in bulb catalogs.
I would like to buy a new one, if they still make them.

Does anyone know the part number and if they will work with a 4 watt ballast and starter?
I would guess so but?

They will undoubtly work fine with F4T5 equipment. In fact, back when GE was making their T5 lamps in the USA, they were slightly slimmer than the standard; pretty close what is now classified as T4. Westinghouse's T5 lamps were similar.

This is assuming T4 lamps don't have any special gas fill that alters their electrical characteristics. There are photos here of them being run on T5 equipment, so it works at least for testing.

Good information, thanks

Does anyone know the part number as I have not been able to find one in lamp catalogs.
Or do they still make these?