The only times that I recall the tectonic knight uniform in official things would be these comic strips:
Which have a few nice shots there, which are the most useful.
It is also in this one, but with less useful looks at it.
Then of course there is the anime adaptation of the linked comics, which can be found by looking for "The Diary of the Awesome Me" on youtube. I don't have screencaps, but you can take a look for yourself!
That is all I can remember as far as official things go without digging into fanart. Though I am not totally versed in the ways of Prussia so I could have missed something. But those might be a start?