The tiny tilt head Manfrotto makes may be a bit too small, although they are fine for ordinary consumer SLRs with smaller lenses. There are a number of very sturdy slightly larger tilt heads likely intended for sports and wildlife photographers with lenses in the 7 to 10 pound range. The platforms are also larger than the tiny Manfrotto head. List of vendors, in no particular order:
Custom Brackets (I have this one, very well made)
Kirk
Hejnar Photo
RRS
Acratech
Sunwayfoto
Maybe Feisol? I have two of their tripods, well made.
As for the leg itself, any stout (large diameter tubes) monopod ought to do. I happen to have a large Induro, which also serves me as a walking stick on hikes. But Manfrotto, any number of Chinese and Taiwanese vendors, Gitzo, RRS, Kirk, FLM, etc etc - anyone who makes tripods also makes a monopod. Carbon fiber if you need damping of vibrations, aluminum if you don't expect to need the damping.