Cabelas carries some from a group called the verminators. I have a few of theirs and have had the very best luck with a solid black one they call thumper. Also look for calls by a guy named Randy Anderson as they are very good also. Both of those guys are reasonably local to me and their calls flat work.
Been calling coyotes for several years now and it is my favorite type of hunting. The open reed calls are challenging to get the hang of but are the best in my opinion. With the electronic callers, what you have is what you get. With the mouth calls you can vary everything to suit any situation.
Doubles are not that uncommon so never say never. I pulled in a triple off one set before I'd ever called a double. Just shows anything can happen but that's where the fun is.
So many coyotes....so little time....