Review on Universal Manual Transmission Shift Knob Shifter Adapter M12×1.25 with Adaptor Set (8mm, 9.5mm, 10mm, 12mm) by XtremeAmazing by Saradhi Suter

Of course there are better options, but they are at least 4 times more expensive than this adapter. It does exactly what you need. I want the bevel of the shift boot retainer to be on the other side of the set screws. The set screws are very soft and easily removed with the included Allen key, which isn't quite the right size. Most of the other options available have the same problems. One of them has a chamfer in a reasonable spot, but the male end of the adapter is too small and breaks easily. In any case, 95% of the shift knobs are M12 and only adapter rings are used to reduce the size, so there's really no reason not to make as many of these as possible.