Courtesy of Bill Stietenroth (Uncle Zed), K5ZTY (sk), NARS has a pair of switchable bandpass filters that enable us to simultaneously operate two stations on two different bands but in close proximity. Several club members have built their own version of this filter for use in their multi-station operations. Thanks to Marty Fitzgerald, W5MF for sharing the information that led to this article and Bruce Meier, N1LN for sharing the pictures of his build of the filter.
The filters were constructed from the "Inexpensive Interference Filters" article by Alan Bloom, N1AL in the June 1994 QST. If you are contemplating building one for your station, you are urged to download the article from QST for tips on construction and tuning the filter. Some design features are not immediately apparent from the schematic.
There is a circuit board available from Far Circuits for $13.50 (as of June 2016). The board is listed under "Miscellaneous Projects and Breadboards" on the FAR Circuits website. The remainder of the components can be purchased from Mouser or Digikey if your junk box is lacking. Probably the most expensive component is the enclosure. N1LN's parts list and tuning notes are here.