Anyone know of any AR retention products out there, something like a "holster" to keep it from swinging around. I once had one made by blackhawk, kind of like a talon-flex deal, but didnt like it.

You mean like a 3 point sling?

Besides the 1-2-3 point sling, an attachment point on the duty belt or Vest works.

BlackHawk (Despise the company, but they have them)  and others have duty belt and vest attachment gizzies the allow for anchoring the fore-end that work.

Look for simple operation that provides a secure purchase during bending and climbing activities.

Simple is best.

I use a simple and recycled  6" velcro ended strap, through a Molly loop on the vest, and wrapped around the handguard.

Coming upward from the bottom and hitting the strap with the blade of the hand breaks it free.

S-28