Changing fixtures or bulbs? Looks like the fixtures have the 921 wedge base bulbs. You can find bulbs from many sources with prices ranging from 75 cents to almost $30. We replaced our 921 bulbs with tower style 250 lumen Natural White bulbs,obtained from RV LED Bulbs (Ocala Hitch) for under $9 a bulb. While these were not the cheapest out there, they fit our needs and wants, were delivered in 3 days with free shipping.
Whatever direction you go, check it out and get what works for you.
2006 Silverado 2500HD Duramax
2010 Prime Time Lacrosse 303RKS
2007 Hensley Arrow Hitch
PT Crew Member 125
Good Sam Club, Cedar Creek Sams Chapter
Passport America Member