I agree slicing is the drudge work in making bacon, no question. The problem is not only that I've been warned against the less expensive consumer-grade slicers by G Wiv (who says the opinion is fairly negative on bbq boards), but even if you thought they were sturdy enough-- and the ones at places like Cabela's
look plenty solid-- the fact remains that they're just not big enough for a whole belly. You'd have to slice from one end until you got the other end down to a width of 9" or so anyway.
I think there are really only the two options, unless you're so close with your butcher that they're willing to let you bring in outside product to slice it while
costing them the sale of the same item: find a used commercial slicer relatively cheap, which is still a several hundred dollar deal, or slice it yourself. My secrets for making the latter more tolerable are: go get yourself a seriously huge slicing/carving knife, I got one at Northwestern Cutlery for maybe $20, and chill the bacon down to near freezing before cutting. The colder it is (short of turning solid), the less floppy it is and the more you can easily cut straight and clean. I usually do two at a time, and so one is in the freezer, I cut a couple of dozen slices, then back in the freezer while I cut the other for a while.