they dont know colour gels
thats a shocker..
well if they are very hard to find or not available a replacement can be found at stationery shops. There is some transparent sheets in different colours for kids. It might not be approx same but would fulfill the purpose in some way.
dont know about the price but it can be rented at cheap rates from local theatrical groups. DIY can be dry ice method and safe too but the smoke is limited.