Pro-Bolt used to sell the aluminum p-clips in various colors, and with 5mm or 6mm hole size. From using them in the past, I know they are extremely fragile/brittle, and they break in half very easily. Probably why they are NLA.
Found out that Pro-Bolt UK has a similar p-clip available- only with a 6mm hole and stainless steel, no colors. Pro-Bolt USA doesn't have them on their website. Plenty of other p-clips also available from different vendors for less money than Pro-Bolt.