OK first off, what all is wrong with your current motor?
can it NOT be rebuilt? as that would most likely be cheaper and easier to get done
if not have you tried doing a online search for one for sale?
have you contact a dealer, they normally know of where top get you a replacement motor/engine, if your is not rebuildable!
(messicks would be able to find you one )
but dealers tend to not be the cheapest option some times
so other places are like
places like EBAY, normally have plenty for sale, and same with other rebuilding or so called re manufactured engine builders selling rebuilt motors or remanufactored ones
sites like this
see below as examples