Where are you located?

If in New York, just do a Google search for camera rental new york.

I know that until recently when the store was broken into, my local camera shop (where I bought most of my equipment) rented out different cameras and lenses.

Ironically, it's the lending of one of my lenses that landed me in the world of wedding photography. I lent a lens to a professional who was considering a 70-200mm f/2.8, and she needed help (last minute) at a wedding on a very hot day in a vineyard.

I helped her out, used my lens, and since then have been doing second photographer duties for her.

Check your local shops. This is one of the advantages to doing business locally with your camera stores, as they are much more willing to rent rather expensive equipment to you if you're serious about trying before buying.