The one I had was made by Rubbermaid. They are made to be stackable or can be used as a single inbox. A Staples or Office Depot type store should have them.
Here is a link to some on Amazon.
http://www.amazon.com/Rubbermaid-48721ROS-Stak-A-File-Single-Smoke-RUB48721ROS/dp/B0017YP14I/ref=pd_sim_op_1?ie=UTF8&refRID=1TGR45BXSZH0RSVKDRTB
I think this is a pic of the one you got from me when I tore that tank down. I bought it from the display tank at Petland.
Here are pictures of the one I got from you years ago. I think you had this monster in your 55g.
Here is another picture of some clams I had. Not giants but around 6-8"
The largest clam I've ever had a shell that over a foot long and when the mantle was extended it was close to 16" long. I don't have any good pics of that one here at work but if you go to the last half of this video you can see it spawning.
http://youtu.be/3trYwrAzsVQ
I have drilled tanks with livestock in them from the inside out. I drain the tank half way down. I used a small powerhead in the tank to provide the water to cool the bit and to also wet down any rocks/corals that are exposed. The drill slurry makes the water a little cloudy but it settles out in a day. No issues afterwards that affected corals or fish. What size tank?
I have a new tank full of dino snot right now. It came in on some frag plugs. Let me know if you want some and I'll bring it to work (Bethesda/Kensington).
Yes, it could be sand particles stuck to his slime coat. If they are still there tomorrow then it might be ich or a similar parasite. How is the breathing? If rapid breathing then it is ich as ich normally attacks the gills first.