You might try a local woodworker. The fine wood dust from a woodshop is probably what you are looking for. He will probably be glad to give it to you for free. Just be sure he is giving you dust free of glues and resins if you are planning to use the compost for food production.
"Never doubt that a small group of thoughtful, committed citizens can change the world; indeed, it's the only thing that ever has."-Margaret Mead "The only thing worse than being blind, is having sight but no vision."-Helen Keller
As Roberto said, any woodshop will likely give you more than you want. If you're in Vermont you can have mine! Definitely make sure they don't use a lot of plywood, or that they keep that dust separate. Also, you may want to inquire about the woods they work with. I probably wouldn't try to compost something that is rot resistant (like cedar) for obvious reasons. If they use a lot of tropical hardwoods, those can be rot resistant as well. And avoid walnut (and some other woods I think....butternut is related), which contains a chemical that inhibits other plant growth.
If your area has any kind of forestry or timber industry, go to a small local sawmill. They will have mountains of sawdust, and you'll know it's clean and safe, probably coming straight out of the pine tree. They may also have planer shavings. I don't know if those would work better or worse than sawdust. They'd be fluffier than dust so might aerate better. But they might not seal in the aroma as well as the fine dust.
Try looking on Craiglist, the local paper, the yellow pages or online for local guys with custom sawmills. (Woodmizers). They produce fine sawdust and in surprising large amounts. With thin kerf bandsaw blades 1/16-1/8th inch, it makes for some really nice nice sawdust for cordwood construction, sawcrete, pycrete and other applications.
We can buy it buy the cord here from the local sawmill, however it is getting expensive due to their own consumption in their boilers to make power for their mill, and because the pellet companies buy it to make wood pellets for that new industry.
As you found out, wood from the utility companies is not all that great. It is easy to get, but I have noticed a lot of people on here trying to use it for the wrong purpose. It is pretty much mulch and nothing else. Since a fair amount of it is bark, leaves and twigs, it does not hold much value. Even in biomass boilers (and I mean industrial sized ones) they cannot burn the stuff, they need what is called "clean chips". It takes a better processor (massive chipper) to produce that which is a specialty of the forest product industry. The show Ice loggers is a great example of what to see regarding what is considered "clean chips".
I really don't think you will have trouble finding a source for your fine sawdust. Good luck!
I did the Humanure experiment for 2+ years. It worked!
I hit on an excellent carbon source, pellets for pellet stoves.
Most of the big box stores like Menards or Lowes carry them for 4 or 5 dollars for a 40 pound bag. The pellets expand like crazy when they get wet, so by volume, they must triple in size at least. Pretty good at minimizing the wet and the mess and the smell.
There are enough pellet plants that I suspect (and hope) that they are generally not shipped very far.
By the way, they make fantastic litter box filler for cats and rabbits and other wee beasties. It is sold for that as Feline Pine, but at approximately 10x the cost. No thanks...