Our good boy needs surgery

This is zeus. He is a 5 year old mastiff mix, and the light of our lives. He has started to have some knee problems, and so we took him to the vet to see what was wrong.  The vet told us that he has a cruciate ligament injury, and the only way to fix this is to have a very expensive surgery that we just cannot afford at the time. Me and my fiance are getting married this year, and are in the process of paying for that, and for this to also get thrown on it's becoming, well a lot to deal with. Any help will be very much appreciated. Thank you so much