That or crappy tire. Just paint it.
What's a vertical grip for the left hand look like?? If you're talking about fore grips you can basically grab them from any hand you want.
Since it's only for a film just get the cheapest from Canadian Tire or Wall mart, they are like a 100$ or less. There's no need to go for airsoft here. It's only for a school film.
If you want other suggestions; there are literally hundreds of threads with new people that don't know about airsoft and they're doing a school film and they want a cheap gun, etc etc...
Besides, if you would like to get a real airsoft gun, you would first need to prove you are over 18 so Just stick with the Canadian Tire or Wall mart guns; much easier to attain and much cheaper.
WE AIN'T DEAD