If you're going to replace them all, upgrade to led and buy a matched set. Like these. look to be very similar to shape and mounting you already have.
Amazon.com: Partsam 14x Trailer RV Marker LED Light Double Bullseye 10 Diodes Clearance Light Red/Amber, 4x2 Tiger Eye/Double Bubble 12V Rectangular LED Side Marker Light Indicators Surface Mount Camper Trucks : Automotive
Or just search for ones you like
Linda S