They really aren't that hard to find -- you're just looking in the wrong place. They're a popular battery for those dog training shock collars as well, and you can get them in 25-packs on eBay for under $20 (or singly for about two and a half dollars). You might not find them in every camera store and drugstore anymore, but they're still around in droves.

That said, a 4LR44 is four LR44s. Whether you can use four of the button cells or not depends on the design of the battery compartment -- if the walls are metal and connect with the end cap, then you'd be bypassing all but the first cell (and potentially shorting out the others). If the walls are insulated from the end connectors, then yes, you'll get the right voltage and form factor (but the first cell in will flip over on you just about half of the time).