Missing orange cover on marker light; Water leakage concerns

Google "Bargman marker lights" They won't be an exact replacement but between the hundreds of options available, I'm sure you'll find something acceptable which has better quality than what you currently have. Just buy the entire fixture (with the bulb holder/wiring) rather a replacement lens.

Check your other marker lights for cracks/water leakage. You may want to replace those too.

Chum lee