Need to know the Chassis Model. Such as Workhorse P32, W22 or W24. Or is it a Ford Chassis. If Workhorse, you can try these few places. One is Oemy's Web Site -
and the other is https://www.ultrarvproducts.com
Some have been able to find at local auto parts stores, and others have just had them made. List the Chassis and a lot more responses will appear. Might want to add what lines he is looking for, such as front, rear, right, left or all. Good luck.