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That's a common implement tire size. And probably a common hub size (though to be sure about that you need the bolt spacing, however, bolt pattern is irrelevant to tire choice).

You haven't defined what you mean by "best" source. Biggest choice? Lowest prices? Tires in stock? Quick service? After hours service? offers you a trading account? It may also depend on where you are and you haven't told us that.

Where I live, most people would use a light truck tire, maybe from a 4x4, and often a good used one. Only the most fastidious would use a proper new implement tire.

Tubeless tires need a rim shape designed for tubeless tires to hold them properly. If you can't achieve a good seal you may need a tube. Look at the nipple. IF it has a grommet the tire is tubeless.

If it were me I would just remove a wheel, take it into my local tire place and see what they say.

Roger