Here are 6 sketches I made last week. Each one was drawn inside a copy of my Mecha Zone 1.5 book as a reward for pre-ordering the book. These went out randomly to international pre-orders. Maybe one of them is in your book?
These aren't supposed to be any particular mechs, just whatever my brain barfed out, but some of them are pretty generic so they may be reminiscent of existing mechs.