Here’s a link to the mini adapter. Apparently there is another company making them and selling a two pack for roughly what Opsal wants for one.
https://www.amazon.com/gp/aw/s/ref=...ip+shockwave&sprefix=opsol&crid=3KC4VX7NATOUO
And if you go to OPSal's website, they claim that the knock-offs being sold through Amazon will fall out of the firearm on occasion.