Baud Bags doesn't let you select the size of the "bags" (I don't think), but it does let you decide which bags to combine into views. Sort of a "multi-OneBag" thing. You could also look at OneBagPockets, which creates unsorted sections of the OneBag window. The only reason I know about either is they've both been mentioned on these forums, and I haven't tried either one.
I think you can use SanityBags to combine "real" bags, in an unsorted way. From the Wiki: "bag:<integer> - matches all items in a given bag. 'bag:1' would match all items in your backpack, for example." I bet you could do a "bag:1 bag:2 bag:3" sort of thing. This is one of many things I comment on without having tried, though. ;)