VERY true, but unfortunately, in the land of TVA, the chances are probably slim to none. I used to be a contractor for them before in the 1990s, and a co worker worked for them after 9/11, and I am afraid any request would fall on deaf ears.
Now, concrete plants do buy "fly ash" from power plants, but I am afraid that may be too fine?
Another (more expensive) thought was a coarse grade of "black beauty" blast media.
I was going to suggest Black Beauty - though you are right, it would be more expensive. The last time I checked (4 months ago) 3000# of the fine grade (60 sieve) was $210, picked up. This was for a pallet of 30 - 100# bags. It may be cheaper if you buy it in bulk. As I use it in a blasting cabinet, I have never even considered not buying it bagged.
Don't know where you would have an outlet near you, but Reed does have a website that should list their production facilities. Black Beauty is processed from power plant coal slag, so it is much cheaper if you can buy it at the source (Reed's production/bagging facilities are all located at power plants to minimize transport costs). Here in New England, Reed sold its production plant in Bow, NH but the independents that bought it still produce "Black Beauty" under license. If anyone is interested, I can post the location and contact info.
Somebody posted a thread a few months ago about using the granules (whatever they are made of) that are used in asphalt roofing shingles. Seems like they'd be the right size, but I don't remember if the guy ever found a source or not.
Check to see if any local road agencies (County, State, Township, Municipality, etc.) uses fly ash (wet bottom boiler slag) for ice control. They may be willing to get some for you. Be careful with the stuff; if the coal is high in sulfer, the dust will be high in acidity, and a speck in the eye will burn a spot in your eyeball that your eye doctor will see for months. (The voice of experience.) We used to use a lot of it. It also can have slivers that are like little needles.