Most manufacturers use off the shelf bearings since it would not be cost effective to manufacture them in house. They may or may not have them made to their own specs and should not be proprietary. Any good supplier of gears and bearings I.E. Timken or INA should be able to cross reference the bearings at considerably less cost than the transmission manufacturer.
tried that for the KK 20x 30x 28 IdxOdxwidth, Timkin, Fag, others no KK bearing. A KK is a double row, needle cage bearing, Even my chinese sources over here couldn' find. In this case they are the only one to have. Spent months trying to find on the internet until " never monday" above gave me that number.
What you say is true about the other bearings and also bought from a bearing supplier.
is there someone who can give me the specifications of the taper bearings, 2 times 2, from a HurthgearboxHBW 250, a very common box. In the past, they worked on the box and, I think, they put in the wrong taper bearings. OD and ID are OK, but the thickness is most probably wrong. I do have 0.8 inch play on the reverse- and forward gear, also too much play on the outgoing shaft.