The sock holder is from CPR Aquatics, they come in two sizes 4" and 7" diameters. Here's the link from CPR, you should be able to find them on line at most online ordering sites: http://www.cpraquatic.com/products/siha.html
I am using about a 1/4 cup only of the Bightwell Carbon and placing it into the sock but in a separate bag (bag within the sock) for easy removal since I change carbon once a month but clean the sock every two or three days.
The sock that I am going to try now is new from Vertex. It is a nylon (not felt) material, 300 microns (4" X 14"). It shouldn't clog up as easy and likely easier to clean. I have not used them yet, I will start tomorrow with the new sump. Ask me again in a week or two and I will let you know how they are working out. The Vertex site is a bit dodgy so I found them on Premium Aquatic site for you: http://premiumaquatics.com/store/merchant.mvc?Screen=PROD&Store_Code=PA&Product_Code=VX-AC-NR414&Category_Code=
I like clear water as well, and with the pre-filter in my canister I had no problem achieving that, I am no longer using the canister. I bought the sock holder a few months ago for my sump, I found that it clogged in a day and was no longer affective, I was using the felt socks, almost impossible to clean, so I gave up and took the whole unit out of my sump and started using floss (threw it out every week or so). So, with the new sump I thought I would give it another try, this time with the Vertex Sock 300 mn. I am really hoping this thing works (I bought two), if not I have an idea to make my own with 500 mn netting.
I am trying to make filtration process simple and less time consuming to maintain. Yet, I want it affective and at minimal cost. I have not met two people who are using the same filtration methods, there are so many DIY and prefab units out there the combinations are endless. If a filtration unit works well for you, don't change a thing. If not, your likely going to have to DIY something to make it work better somehow.