Where Can I Get A This Thread Adapter In The US?

Eagle Vision is crazy cheap for a $14.99 Vulcan threaded barrel adapter at AoA. Maybe works for the Uragan but haven't even unboxed mine yet but have the AoA Vulcan adapter separate order before that for one of my Vulcans.

Thinking of ordering more to mod them to work on other guns for cheap.

https://www.airgunsofarizona.com/airgun-silencers/eagle-vision-vulcan-1/2-unf-muzzle-adaptor/

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No it's for a Vulcan but you may get it to work if it's slightly larger than the Sig threads by sticking a proper tight fitting non metal fiberglass or straight (roll it on a flat surface to check) but round wooden dowel rod tight in the end of the barrel to center things then epoxy or JB Weld or plastic glue gun it if you don't want it permanent.
 
You use a perfect fit bottle cap with a hole perfectly drilled in the exact center the size of that dowel to keep it centered while glueing it to the pistol. Be sure the specific LDC won't clip when attached by sticking that rod in while attached before taking your first shot make sure it's centered at the exit hole of the LDC otherwise you need to reposition it.