Has anyone seen this for sale?

[dscoduc]

While looking at a Sig Sauer AR Pistol the Bolt Catch was different than I had ever seen. I really like it but can't seem to find anything like it for sale... Does anyone have ideas on where I might find this for sale?

You can see where the bolt catch has a 90 degree angle and provides a finger place to hold the bolt open when no magazine is inserted...

[CK_32]

I haven't seen it for sale but I saw a full article in last months Trigger or Recoil mag. One of the 2. Looks like a pretty fun little toy. Probably not worth the $$$ it probably costs tho.