As often happens I was looking for something, (LED marine lights [the RV industry has not yet gotten the message in the US]), and on the way found the solution for another problem.
When you tack on the RV appellation, the price goes up by orders of magnitude all out of proportion to the quality of the item. To put it simply I hate paying inflated prices for cheep junk.
I have been looking for a way to get the air conditioning hoses through the side of the teardrop and every single one I could come up with was just plain butt ugly. On the way to marine lights I discovered deck plates in various sizes (including the four inches I need), and various size hatches, and drink holders… at a reasonable price. I will give only one url, this will give an idea what is available (there are other sources) and encourage you to look for other marine products that are adaptable.