I don't know how many kits may be available since Hartland Locomotive Works has announced it will cease production indefinitely, BUT the HLW two axle flat car bears a close resemblance to the cars in your initial photo. I know Reindeer Pass had a fair number of those kits, and they are very reasonably priced. You may want to give Mike a call or check the store's web site.
Regards, David Meashey
P.S. Here is a blurry photo of one of the cars I was working on for another project. The metal wheels were added after the fact. the kit has plastic wheels.
I think they are LGB ball bearing wheel sets that I bought at a blow-out price at an ECLSTS show many years ago. I prefer metal wheels since they seem to help keep the track cleaner, but as my interest has turned to #1 gauge live steam - clean track becomes a moot point.