If you're rural, you're likely asking parents to come up to a school on a night when there are chores to worry about. There are ALWAYS chores on a farm/ranch. They can't just not milk the cows/feed the horses because the band director wants to have a parent meeting or there's a football game.
See if you can have the meetings on Sunday afternoons or another time that is more neutral to their schedules. See if you can arrange for food to happen - do a hotdog cookout or something. Don't call a meeting for 7:00 on a Tuesday night and expect parents to be able to drop everything to come back up to school. Same with chaperoning - just move the problem to Friday night. You're going to have problems in rural areas no matter what.
Also, since we live in the age of this, consider holding virtual meetings. You may get more participation if parents can login from home.
As for getting more - many rural parents right now are living right on the edge of financial ruin. They may simply not have any money to give you anything. Build the cost for snacks/drinks into your band fees or find a way to get it sponsored by the local store/feed supply place.