Have you considered using pellets? BBQr's Delight makes pellets in about 15 different varieties. I use it regularly in my WSM, much more often than I do chunks, in fact. Just did a
tasty smoked salmon using the alder pellets. I would NEVER have found alder around here otherwise. I was lucky enough to be one of the testers when these were first coming out, and have been using them ever since. A BBQ/fireplace store here in the Tulsa area carries all flavors, and I'm a frequent customer. I have ordered from the site, as well, and have gotten excellent service. You can buy 1-use bags, but I usually buy the 10-use bags. Just takes about 1/3 cup for each cook.
BBQr's Delight Smoking Pellets
Have you tried calling an orchard and offering to trade them a slab or two of ribs for a couple of big deadfall or pruned branches? On a WSM, a big branch lasts a LONG time.
Keri C, smokin on Tulsa Time (with alder, cherry, apple, sugar maple, oak, orange, Jack Daniels, mulberry, hickory... )