you'll have to fish around to find where, but per the schematics- clearance light power wire should be marked 1008, and ground wire marked 1435. The ground 1435 wire is common at some point (the schematics show what is connected to what, but not where the connections are in 3-space) with AuxFans, remote gen start, gen hour meter, & TV override switch.
If those other functions are still operative, I'd assume for the time being the ground is made & trouble is on the 1008 power feed wire. The clearance lights are in parallel, so if any one bulb burns out its not like an old Christmas tree string, the remaining lights should still operate; so if all are out the trouble has to be either in the 12V feed on the 1008 wire before the lights, or in the 1435 ground between lights & the next splice w/the above circuits that still work.
I know there are wire bundles in both my driver's & passenger's windshield side posts; probably also in yours. I think this is where the wires run, but YMMV, could be up the center post; perhaps somebody who has performed this spelunking can chime in.
1008 appears to be fused by the ParkLP fuse off the Parking Light Relay in the Battery VEC, ahead of passenger's feet behind plastic kick panel.
Baja-tested '08 2-slide 36'
Alpine: The Ultimate DIY'er Project