Thanks to some recommendations here, I checked out a variety of custom floor mat brands. The only one of the many recommended that appeared to be available for the Ridgeline was the Husky Liner. I ordered a full set, with a net cost of about $140. I've used them for a few days and here's my report.
The liners are nicely custom designed for the front and rear. They are something of a rugged, plastic tray, with high sides and more or less flat rubber bottoms. They fit pretty snugly, although they were mailed folded over and have yet to fully recover. You could probably pour a gallon of water in one of the front ones and it wouldn't overflow. The carpeted floors seem well protected.
If I lived in a really muddy environment and was wearing boots all the time, I might like this design. Unfortunately, or fortunately, I don't. I live in a very sandy environment and wear mostly sandals, if that. Each time I get into the truck I track sand, which sits in the bottom of this tray and slowly piles up, so that my feet, sandals, or shoes sit in sand. This means, also, that each time I get out of the truck , I track the sand around wherever I am. Bottom line, these Husky Liners are definitely husky and they are definitely liners, but not really what I'd prefer for my application. The are definitely an improvement though, over the factory design, which has relatively low sides and doesn't fully cover the carpet.
I checked out the WeatherTech liners and, for my purposes, they appear to be a much better option. They appear to have rubber channels, of sorts, sticking up so that your feet are above the sand and grunge that goes down into the bottom. I've had mats of that nature before and it allows you to keep your feet clean while the sand and whatever is removed by gravity until you decide to shake out the mats. Unfortunately, the WeatherTech mats don't seem to be available yet for the Ridgeline. If someone knows otherwise, please let me know, but I ordered from one website, which disingenuously implied they were available, and got an email a couple of days later saying not.