Gee -- why not start right here on iBoats since they host this forum. They have what is probably the largest selection of props anywhere at very fair prices and depending on model, they even have "try it" program. They also have a prop calculator that you can plug numbers into if you are unsure of what you need. Click the MARINE STORE button right under the iBoats logo at the top left of the page. Sometimes the panel at the right has prop ads as well.
H2oBoy, I bought a SS Prop from iBoats fro 1/2 the usual price. They had a special. Alternatively, you can go used or adapt a prop. The Merc prop's will fit an OMC outboard, with a minor modification.