The articulated well cars from A-line are starting to appear from Intermountain, first issue is the Thrall 40' well five unit set in TTX, as pictured here on the Intermountain website. According to Walthers, an APL version of that car will follow, with the Gunderson TwinStacks also due to arrive in TTX, SP and Conrail schemes.
I think they are going to start doing some of the pup trailers as well. I better hurry up and finish my twin stack, before the RTR hits