What spray do i use to seal an outdoor garden gnome?

I have a garden gnome which I have repainted using ceramic acrylic paint. I had a tin of matt acrylic ceramic spray but it is finished. when i have went to local shops they have sold me plastikote fast dry enamel spray but i am unsure if it is the correct spray. i do not want to use it if it is not waterproof or if it will turn my gnome yellow. please help.