A modified Prusa bar clamp that is able to slip onto both threaded and smooth rods without need for vertex disassembly. Since M8 & 5/16" are so close (8 mm vs 7.938 mm), these should be usable with both metric and SAE.
Unless you are feeling lucky, I'd recommend using the beefy variant.
1 - Print
2 - Replace
standard prusa: 2.4g - 15mm x 15 mm x 25 mm
slim 2-way: 1.8g - 15mm x 15 mm x 25 mm
beefy 2-way: 2.49g - 16.6mm x 16.6 mm x 26.6 mm