As Chris noted, example of Snap-On Lens

And Lamp-from-Behind

Daughter's Terry Hybrid trailer has the from-behind's. I went to get lenses and found I had to get complete lamps. Nice thing, I think the sockets for the 194's are a little better. Bad thing, have to use sealant to replace the bulb.
Betcha you can pull the lamps off and use your LED 194's. Just have a tube of Dicor non-leveling sealant handy. Friends Don't Let Friends use Silicone.
Just pray the OEM didn't rivet the lamps to the coach! Seen that too, but at least the lenses came off to change bulbs. Those were the old "57" bulbs and the contacts were terrible. Lenses also started coming loose. New lenses wouldn't fix it, since the plastic bases had shrunken. Ended up drilling lens and using a small stainless screw into the base.