Ok, site address is.
The tire you want is under BICYCLE, and is part #TB35786000
Known as the "Maxx Daddy" and it's a pretty good tire, tho the tread is more aimed at motorcross than street use.
They run $15.99 USD each, which is pretty good fer pricing.
As for tubes, if they need tubes (might be tubeless), try askin Maxxis, or going with the BELL self-sealing.
Best of luck,