Yeah, short of buying a rep clasp n strap off of Shopee or sumthing, best bet is to go back to the AD or RSC and get it. PRicey no doubt, but at least u get the gen article.
A side note: My experience trying to get my hands on parts, it was rather annoying - I wanted to get some spare spring bars and they were asking me so many questions it was like an interrogation. Maybe straps are easier to work with, I dunno, but give it a try.