I don't have a spare, but a bit of brass or steel pipe, a thumb screw, and
the appropriate tap and you're there. You can squeeze it in a vice to get
it oval. If you don't have a tap, you can solder a nut on. Lots of
options until you find something better.
Nothing wrong with pinch locking or wedge locking home made router planes
either. You can grind a useful blade out of a large Allen key. Drill a
hole in a block of wood and stick an old 1/2" chisel in at an appropriate
angle and you're good to go (that's what I use by the lake, a bit of cut
off 2 by 4 and a narrowish chisel).