You might try calling Heartland Customer Service after the first of the year.
If you'r coach is a couple years or maybe a couple months old they may have changed lighting styles or supplier. It might be worth a shot to give them a call.
If they don't have the part they might be able to direct you to the supplier. Have the last eight digits of your VIN handy when you call.
You might even check on eBay.
Heartland Customer Service 877-262-8032 .
Peace
Dave