Does the 99 Rodeo have the rectangle fog lights or the more oval/round style in that bumper slot?
If its the round style you can get a kit at the dealer. The kit includes two 55 WATT projection fog lights, mounting brackets, solonoid and a dash switch. Everything was plug and play on my 01 Rodeo. The only problem I ran in to was the dash switch. Isuzu had to special order one for me since they changed plugs in 02 or 02.
My plug had five pins across [.....] the switch in the kit looked like this [...:] I'm rambling
Why not just find some fogs and the local autop parts store that have the same dimension as the factory fogs and then just splice into the factory wiring at the mounts? Seems like it would be pretty easy. Then you could just buy the switch and the relay from the dealer. There is also some wiring FAQ's on the net regarding changing the ground so you can run the fogs through the factory switch with high beams on. I did mine, and I think it was the yellow wire going to the switch that I had to ground, but mine's a 2000 and don't know if they changed wire colors from 1999. There is also a FAQ out there somwhere that allows you to bypass the headlights and run them with only the parking lights on.