What can I use to substitute Acrylic Paint?

I need white acrylic paint. I've been to 4 craft stores and none of them have white acrylic paint. I was thinking of what can I use to substitute acrylic paint. Have any idea? I am going to use it on a paper mache project. We are not allowed to use poster paint.What can I use to substitute Acrylic Paint?
Gesso will substitute for paint in this case, also white latex primer for house paint. Spray enamels won't allow you to use acrylic paint on top of them.What can I use to substitute Acrylic Paint?
That is very odd, I have never seen an arts and craft store without loads of acrylic paint of all colors. Try to go to any warehouse type store, to find the acrylic. (ie Walmart, Target) If not, I don't know how small the detail in white is going to be, but if it is just a background color grab a can of spray paint.
I agree with Joyfulpaints Gesso a good substitute
Acrylic paint is water based so try to use any house latex paint or any other water soluble paint, though other water soluble paints will not have the same covering power or mixing power as acrylic paint because of lower pigment amount.
I'd use white spray paint or enamel if tempera is not allowed. ';poster paint'; could mean anything...but your instructor probably means tempera