We bought the Mystery Ranch hands-free sling and Eberlestock Buttbucket+ripcord from Blades Canada in Vancouver. Both offer "quick detach" from behind you but the Mystery Ranch is more elegant. Blades Canada is sold out of the Mystery Ranch (sorry, I must have bought the last 2), but you can call them and ask when they are going to have inventory again.
https://www.bladescanada.com/Mystery...-Sling-Foliage
https://www.bladescanada.com/Eberles...itary-Green-HD