Where do you go to get portable restrooms

I have been put in charge of finding a vendor who rents out portable restrooms for my sisters wedding. My mother thinks we need to have at least four portable restrooms available for during the ceremony and reception with at least one of them being handicap accessible. I guess, we would also need hand washing stations as well. I don’t really know where to start looking for companies who provide such a service, especially out where the wedding will be. If you have any experience on this topic or have any suggestions, please let me know. I really don’t want to have bathrooms get in the way of my big sisters big day.