It kind of works the other way: NFPA 1192 Standard on Recreational Vehicles says that only listed electrical fixtures, appliances, equipment and materials that have been labeled by nationally recognized testing agencies are allowed.
You can't find any fixtures with screw connections listed.
That's because screwed connections can back-off under vibration.
As far as the UL/CSA certification, just look on the device. Certainly the Hubbell-Wirecon self-contained devices are certified, as are virtually any other you can find.