Don't limit yourself to RV places for the doghouse cupholder attachment. The same basic parts were used on all the E-series vans, so far as I know, and there are millions (I think literally millions) of them out there. The general styles from Ford only changed every few years, so a bit of online searching should show up the factory possibilities and probably ones for sale on places like eBay.
Avoid the '98 version...I have one, and I am pretty sure it's the least useful layout of all of them. There is a very big bucket of a compartment (which is deep enough that it's hard to sort things out), a single cupholder with two interconnected holes, neither of which really fits a lot of modern cups well, an ashtray for quarters for tolls, and a little shelf way down near the floor to hold your cell phone out of sight until you go over a big enough bump.