I can 100% recommend the Troy Lee Designs "Shock Doctor" range. The lightweight range includes guards for knee, shin, knee&shin, elbow, and elbow&forearm guards. Brilliant! Sadly they have stopped making them!

But TLD are still very much in business and they will have a replacement, I just don't know what it is. When I saw signs of the range being phased out I stocked up, so I will be OK.

I have attached a link to some TLD knee&shin guards fso that you can see what I'm on about.
<div> The Troy Lee Designs 5450 Knee Guards - Long provide essential protection for the knee and upper shin in a light and airy package. </div> <div> </div>
www.cyclesolutions.co.uk
PS: As with all guards, check the max temperature on the washing instructions if you want them to last. But with the high tech washing tablets these days, you can wash at 20 degC, just add a laundry disinfectant.