Funny you should ask about this. I was just looking at tires for my ride today. My search was online and specifically for oversized tires, so your results may vary. Here's what I found: cheapcycleparts.com has a set of Pirelli MT66 Route for $171.10 plus shipping. This is a 110/90-19 front and a 170/80-15 rear. If you go with a stock size and a different brand, Dunlop for instance, your cost should be even less. Metzlers are high end and carry a heftier price tag.
Other sites had my tires for slightly more ($171.98) at motorcyclesuperstore.com and rockymountainatvmc.com.
There are quite a few posts in the archives here about tire choices, brands, sizes, etc. and lots of helpful folks on this forum I'm sure will chime in, too.
Good luck in your search.
I'm bad with names. May I just call you dumb?