must it be dual tracking? I'm not sure those exist.
I have a pair of the ones mpwi linked to above, and plan on using them to troubleshoot a beta22 board or two really soon. Obviously, I won't be able to dial in the boards, as I'd need the final supply for that (due to the fact that you sorta get what voltage you get with the sigma22) but you can put them in current limiting mode and fire up a iffy board or two with them...
I'm trying to envision a "dual" supply that wouldn't work (i.e. these "mixed reports"), perhaps you have a link?