norwestie-
if you're willing to pay the price, here's
a link to "authentic" Monaco replacement fog light housings (with connectors). They may or may not work on your coach.
I recently replaced a bulb in my coach's driver's side fog light. Along the way I researched new housings. I found some made by Hella. Here's
a link. It's hard to remove the fog light from the cap on my coach's driver's side (there's a beam immediately behind the housing). The Hella 450s appear to be slightly thinner, and so may be easier to remove and replace. If I break a housing, I'll get a chance to find out.
The size seems somewhat common. Make sure they fit your coach. and/or buy them from someone with a decent return policy.