Aarron makes the collars not the coupling links he just supplies them with his collars as does Jim from blackdogtrading and, i think, Glyn Jones. I have a set i bought off ebay, mine came undone when the dogs got taffled up so i don't use tem anymore and have never used them on tethered dogs whilst out working.
Imo the only time quick release couples actually have a reasonable use is when you couple up 2 dogs inclined to fight each other