I used to work in an office, and there actually are these HUGE black binder clips, like 4" long, that could possibly work. Only problem with those, is that when stressed, they have a tendency to snap off- not good when you've got a anxious snake pushing against a lid.....

With the nut and bolt idea, all you'd need is a very very small screw so you wouldn't spend too much time twisting the nut on and off. Thats how we secure most of our larger boids in tubs at my work.