Lizard Skins makes a great knee/shin guard as well as elbow/forearm protection. I recently purchased both and couldn’t be more pleased. You can find them much cheaper (Ebay) than what is listed on the website. The plastic is VERY hard and seems to be extremely durable.
Knee/Shin
[url:3m6nox4x]http://lizardskins.com/products/view_product.html?type=mountain&product_line=protective%20gear&product_id=97&name=SOFTCELL%20Knee%20Shin%20Combo&name2=&page_number=1[/url:3m6nox4x]
Elbow/Forearm
[url:3m6nox4x]http://lizardskins.com/products/view_product.html?type=mountain&product_line=protective%20gear&product_id=103&name=SOFTCELL%20Mountain%20Elbow%20Guard&name2=&page_number=1[/url:3m6nox4x]