My first thought was, gee these are recent production cars... how did they get broke like that?
Well regardless Steve, unless RMT made alterations in the tooling, these are the same trucks used on the K-Line Train-19 rolling stock, as well as some other later production K-Line cars. You might check with Brasseur as they received the remaining K-Line parts inventory. You're going to need the knuckle, the spring, and you might also want a new rivet for each damaged truck.
I think Lionel also used these trucks for a short while on some of their K-Line by Lionel cars. So you could possibly check the Lionel web site using a K-Line by Lionel rolling stock number.
http://www.brasseurelectrictrains.com/service/kline/kline.php
When RMT was bannered with Aristo, they had RMT parts listed on the Aristo website. You could also try contacting RMT to see if Walter has the parts.
If you already had a bunch of various coupler knuckles around, it's not impossible that you might get a knuckle and spring from another brand to work. I've replace K-Line plastic knuckles with Lionel ones, but you need the Lionel rivet as there's a difference between the diameter of the two rivets.