The sling is going to be tactical intervention. Check out their website and they have a slew of gear. The tan web/cuff sling was implemented part way through the use of the a3 and through the use of the a5 (not sure about the a6, that was after my time)SKU TIS-QC . Maybe check ebay for one that got lost from the armory? As for bottom metal, PTG is a close affordable option if youre looking for a cLone and its mag release is very similar, but I do recommend shelling out the cash for the badger stuff, as it is more aesthetically pleasing, it's 100% proven, and they take care of their customers. When slowly putting together a clone, like the guys mentioned before, an action or stock is a good starting point. With those parts you can at least bed it and upgrade other parts down the road. But if you bed the bottom metal as well, that kind of makes it a pita to upgrade later.