The technology has improved enough that having a projector is a very affordable product for most companies. It is an excellent investment for you to make, and could potentially be donated if you ask the right people.
Because different venues have different needs, I do not carry screens for rental. Screens may be made of basic non-reflective fabric (such as muslin) available at most fabric or art supply stores. A basic frame can be made from many light materials which are rigid when mounted, or perhaps flexible. You just want it to be completely taut when expanded. The absolute best possible material is movie screen material, if available in your area or by special order. Doing a search for “Projector Screen Fabric” on Google or Amazon will yield many results.