Yes, they do make a 1 piece I think it's the sm0130 Of course, it can't really be called a "one piece" due to the adjustability aspect...
That's a good idea, heck, even just fill it in with some jb-weld or other putty type epoxy... heck; I might just do that anyway for everything -- that'd lock it down for good! Sand it and then re-paint it -- no one would know....
re; one piece - well; take a look at the pdf from sun optics -- they seem to list/show it... I found it on amazon; so I suspect it's just people using the generic descriptions...