There is no American counter part.
It might share some of the same parts as one but that's going to be a hard thing to nail down.
The engine might be the same as a a model Bxxxx, while the transmission will not match anything we have, and the rear lift might match a BXxxxx
The bulltra series is very hard to get information on unless you speak Polish and Russian, which seams to be the markets they were made for.
US and Canadian Kubota dealers will not sell you parts for it, unless you don't tell them what it is and you supply the part #'s.
And all of the online parts dealers I know of will not have specs either.
The best thing you could hope to find is a copy of the parts manual and the WSM for it, but there again probably in Russian, Polish, or other language.