The U 1400 has steel side plates. You are asking for those? They are made from standard profiles, but you can also buy original in Germany.
I am more dedicated to the old Unimogs Boehringer 70200, 2010, 401 and 411. But I may can help you.
Check this web page and the pdf file for download.
http://www.archus-neumeier.de/unimog/Neu_erstellt/index.htmlMarkus