Erwin,
It seems 10.50-16 tyres are available in a suitable - though not identical - pattern. See the thread
9.00-13 Tyres for more information.
Would you happen to be contemplating the purchase of that D15 offered for sale by
Camo? Nice truck, I wouldn't let the non-availability of the extact tyre tread put you off from buying it!
Regards,
Hanno