Help - need ideas for dealing with manager

Oh the joys of dealing with the public. lol It can often be frustrating thats for sure. The customer is always "right". lol lol
You can out on a limb all you want, you are never going to make everyone happy all the time.

I have attended and assisted with MANY different obedience and agility classes and I have NEVER got anything free nor did any of the classes I assisted with hand out anything for free.
One class I took (actually 2 classes but the same location & instructor) was through the local humane society. In that class we did have free treats BUT they were free because we the students doanted them. Our instructor was not afraid to ask for donations either. (it was a little different though as it was through a privatly owned shelter). Maybe politely ask if anyone could donate a bag for the class to use when you do demonstrations.

I honestly thought that you the student always had to supply your own treats, leashes, collars, clickers, and whatever else is needed (besides actual agility equipment in agility class).

If you can't get anywhere with them I would just deal with what you have. It won't be long before people start dropping out or stop signing up for new classes. Maybe your boss will then see that they need to do more.

The idea of upping the price $5 or so is a great idea. Take that to your manager and see if they can include a clicker if the price is higher. After all a clicker only cost $1, thats $4 profit for them.