You mention "outlet" but didn't say what you're trying to accomplish. Our 1992, 29' Classic / Excella is likely very similar to your trailer. There is no 120 VAC in the overhead cabinet area on our trailer. There is 12 VDC to run the lights and the radio.
Lucius and Danielle
1992 29' Excella Classic / 2010 Interstate
2005 Chevrolet Suburban K2500 8.1L
2018 GMC Sierra K1500 SLT, 6.2L, Max Trailering
Got a cooped-up feeling, gotta get out of town, got those Airstream campin' blues...