I dont see whats wrong the icon field armor knee/shin guards.
I wear them under pants no problem. Everyone whom I've showed them to didnt know I was wearing them prior. They fit snug nicely into a motorcycle boot, which helps keep it in place from sliding down your knee incase of sliding on pavement. The velcro also helps keep it in place. If you have fat legs, stay away, but other than that.... they're the best bang for the buck IMO.
The Icons look good but they are $60+ US, a lot of the Motocross ones are coming up at about $20 US and look OK too.