I kinda doubt the rim is 1.5 in OD. Just measured and my dh rims or the rims on the DJ are around 1.25in OD.
Anyways here are two examples. Bontrager has 28c tires on a little under 1in OD rims.
Fischer has a 1.5 up front and a 1.9 out back. I prefer the 1.9, and off roading it grips pretty well for fire road/hardpack. Rolls fast at 55-60psi on the rear.
I would look for something like that with continuous center knobs and some knobs for cornering like a conti race king, kenda small block 8, or michelin dry country 2.
1.5-2.0 would be the size I would go for.
