I bought a second cap for my TSE 17, dismantled it, applied a Dremel and added an 82mm wide angle adapter. With care, you can set it up so that filters have about a mm clearance from the front element. This arrangement works fine with some caveats.
1. As others have commented, the amount of shift is limited before the filter vignettes the image.
2. The Lee CPL filter can't be used because it is mounted outside the filter holder and casts a circular shadow onto the image. If you need a PL/CPL, the Fotodiox version is the only route I know of.