For 3D printing I would recommend the models posted on Shapeways. Most of them are free to download, you just need to create a free account.Really nice job Rafal!
Is this the best knee armor version aviable: https://3dwarehouse.sketchup.com/model.html?id=f6bc8ece-dc84-4dc2-b66a-1c85dace6c8b ???
I haven't found any better one. Plan to get printing them soon.
I have 1kg of ABS and can use my Uni's little Makerbot haha.