I just went through the same thing trying to find one for my Monaco LaPalma and I was surprised to discover they are very hard to find! I made a recent trip to Florida and stopped at an RV Salvage yard in Kentucky thinking they would have stacks of them to choose from but the only ones they had were burned from a fire or were from DPs and not suitable for our gas V10's.
Finally found a beautiful one made of oak on EBay and snatched it up quick. It just arrived and I will be installing it shortly on my engine cover.
Before that; I looked at AutoZone and Advanced Auto, etc. and even checked JC Whitney's catalog and found nothing suitable. Good luck in your hunt!!