Still, another size in the Cresta may work. Those boots come in three widths, and the last they're built upon seems exceedingly well designed, meaning it "fits" a pretty broad swath of people. So with luck that will work.
Otherwise, all those things that you apparently don't want to fool withinsoles, thick socks, lacing techniquesare your next-to-last resort. Insoles in particular can make a big difference. I think just about everyone should swap out the factory insoles, which really are pretty lousy even in expensive boots, and install an after-market one such as Superfeet ($30; www.rei.com). The Superfeet people make a "high profile" that's designed to soak up extra space. And, no harm in wearing some extra socksI used to do that on a regular basis before I started to find boots that fit. You can also lace the boots in various ways to tighten them in one direction or another. You'll need to find a really good boot-fitter for that, though.
Otherwise, your choices are to buy custom boots or customize stock boots. Custom boots include Limmer boots, though these will set you back $560 and take a patience-enhancing 42 months to land on your doorstep. A lot of dough and a long wait, but a lifetime investment, too. You may also be able to modify existing boots, particularly in the heel area. A good boot repair person, such as Dave Page in Seattle, could take a pair of leather-lined boots, disassemble them, and add additional or thicker leather to the heel area.
So there you go. Hope you find something that works!