I think you should spend some time looking around. I've got a list of bookmarks for various N manufacturers. Many are not carried by Walthers. Sometimes you need to go to different on-line retailers to find things or dirrectly to the manufacturers. For instance, a look at AMB (American Model Builders) website lists 7 station kits, SP AT&SF, NP, IC and ?? prototypes. Now theses are laser kits and not plastic but fine kits indeed.
On another forum someone was lamenting the lack of "old" gas station availability. In the responses there were 9 or 10 different ones listed. I researched them for current availability and found them in various places on the web as well as a few more.
As for the power plant, I drive past several on I25 in Colorado and the kit that screams at me is the Superior Paper Company from Walthers. Kitbash time. Kitbashing will get you a lot of what's not out there.
My personal gripe is for Produce warehouses. The Central Valley of California has tons of them, rarely two alike, made of concrete, stucco, wood, metal, concrete block, stone, and anything else. Few are available. but I've got some kits I'm goin to use to kitbash some.