A couple of questions:
Have you visually verified the size physically or are you reading what the
manual says? I'm not asking this to be an a$$hole so please take this with
a grain of salt because I've been in the tire business for 44 years fielding
millions of phone calls and sometimes people don't bother to look at the
tires themselves or they look and because in most cases with tractor tires they're very old sidewalls scuffed up making it difficult to read etc.
What brand of tires is on it now?
Is your tractor 2 wheel drive or 4 wheel drive?
When looking for tires your first call should always be your local tire dealer
who specializes in selling tires. The majority of these dealers will do everything they possibly can to sell you tires, that's what they're there for
and with that in mind it's best to let them do all the work locating the proper tire for fitment/use and again the majority will do so at a very competitive price because they want you and your family and every friend
you've got coming in to them repeatedly. Tire dealers have the connections
to get product so give them a call and see what you come up with.
Special note: If you're in a smaller area and there's only a couple tire dealers around please save them all a bunch of time by choosing one and giving them a day or two to see what they come up with, and preferably one that specializes in farm tires or at least commercial type truck and loader tires. Calling 5 dealers in a small area will result in those dealers calling multiple (same distributors ) distributors wasting a bunch of time
best used on another customer that needs tires or service.
Al