Ive looked into Lowepro's system, what with the belt and straps and spots for their pockets. It just seems too pricy for what it is. Ive also looked at several "photojournalism" setups, including various belt-mounted and shoulder-mounted bags. Those seem to fit the bill rather nicely.
Lowepro has their Classified AW series (
http://www.lowepro.com/classifiedseries). You're likely looking at something like the 160/200