If you have a 3D printer, another option is to search Thingiverse for printable designs. I have
one that I've printed (but haven't yet glued together) that cost nothing but printer time and roughly half a spool of filament. Takes standard film holders or Graflok accessories (like Grafmatics), 25mm projection distance (or I could design an extension board to get another 5-10 mm without vignetting, I think), and the lens board can be installed in different positions to give straight view, rise, shift, or rise and shift.