Project Appleseed

If you have a 3D printer and need some 10/22 10 round mag couplers, give this a try:
https://www.thingiverse.com/thing:5960380
Recommend turning them on their tall side in your slicer and printing out of carbon fiber PLA with 100% infill.
They snap and hold together nicely, for a permanent bond a dot of epoxy can be used.
Way cheaper that buying the high dollar ones online. They may have cost me less than 2 cents each to print!