These are probably "too old" for Big Boy now (i.e., too many small parts). But here is what is available.
A nice roundup at HubPages
Cuboro - Swiss, modular, beautiful, and expensive (but there is even a trampoline add-on!).
Old Fashioned Toys - check out the Archimedes model!
Haba has a ball run
Just Think Toys makes a tub version called Waterblocks
DIY Run at MOMMade