Christian, as suggested by dknelson, contact the Union Pacific Historical Society. Their magazine, "The Streamliner" had an article entitled "USRA Mikes" by Gordon McCulloh that ran from page 4, to page 12, in Volume 1, Issue 4. There is another article by Gordon McCulloh entitled "Heavy Mikes" in Volume 1, Issue2. Because the earlier article is specifically about the "Heavy Mikes", Volume 1, Issue 4 might have what you seek.
The list of back issues may be found at https://uphs.org/ Some historical societies publish equipment drawings as supplements to their magazins so, if your interest in the UP is deep enough, consider joining the society. Most groups make special efforts to assist members outside of the U.S.
The UP had original USRA light Mikados and as delivered the engines were pretty much alike - so the drawings in the Model Railroader Cyclopedia Vol 1 - Steam Locomotives should suffice. Changes were made over time so detailing photos would be useful. I suggest seeing if the Union Pacific Historical Society has ever published articles about the USRA Mikados in their excellent Streamliner magazine. Just be aware that it is easy to get confused or misled by photos taken at very different points in time.
The UP and subsidiaries had 2-8-2s prior to the USRA, and I assume they too would be considered "light." See this useful roster
http://utahrails.net/up/up-mikados.php
Again I'd say the UP Historical Society is probably in the best position to steer you in the right direction.
Dave Nelson
Hi, can anyone give my advice for drawings of the light mikado´s of the UP?
Thanks forwart!
Christian from Germany!