First we need to know what kind of lights. .. LED or incandescent? If incandescent, you might be able to find a lower wattage bulb in the garden section of a home improvement store. If LED, it's more difficult. You can get 12V PWM LED dimmers for about $2 on Ebay that you can install in the line, adjust, and then hide above the fixture. On the oval LED fixtures, usually, the cover comes off by squeezing from the ends or sides to release the hooks from slots on the inside of the rim on the base but that's a really difficult bulb to find.
2015 Rockwood Signature UltraLite 8282WS Platinum, GY Marathon LRD, TST 507RV TPMS
2005 GMC 2500HD CCSB D/A, Curt E16, Prodigy P2, Garmin RV760LMT w/BC-20 b/u cam