I have the TWM setup, and I thought the dimensions you guys were giving were a bit small. I measured mine and got the dimensions in the pic. At 3 1/4" at the lip, I figured the strainers were not going to work out for me. I went on a Google search for "tea strainers" and got a lot of hits. Unfortunately, there were few that would tell you the size other than tell you it would fit the rim of a cup. After a while I found this site.
Tea Infusers, Strainers & Accessories
They give you the different sizes of the strainers. Some in two or more sizes. There are a couple that will work out, but for attaching them I think it will involve a tiny sheetmetal screw in the rim. I don't have any fabrication skills for fitting a rim to the stacks. So I will have to use either some silicone or the screws. Some of these handled ones might be altered to use part of the handle as a hold down???
Bill