Pierre and List,
I bought a dozen pair of the Life-Like of Canada Simplex Bolster trucks when they came out in the fall of 2004 from Canadian Model Trains Inc. in Mississauga, Ontario.
The part number at that time was 433-212560 and the description was as follows: LL Proto [1938 AAR Trucks With Simplex Bolsters (PR)] [Used On Rolling Stock from 1938 To Date In Canada & The USA]
If the group's archives go back to about that time there was a long discussion regarding these trucks and their suitability for use with the various versions of the Fowler and dominion cars.
You may try them to see if they are still available. CMT's number is 1-866-862-7277 and ask for Steve. I have just bought Sylvan kits and the Canadian Rolling Stock Series soft-cover books from them.
7 Boundary Road, West Branch
Newark, Delaware, 19711-7479