Yatagan bayonets are actually pretty traditional for old-school 18th or earlier 19th (here's the trick) salawar yatagans. Before they became so wide-based, they already had the double curve.
Do you know what a sumpitan is? It is a Bornean hardwood blowgun drilled from one piece by a two-man team (Amazonian blowguns are bound up out of two hollowed channels), and scarf-joined to its tip is a whipped-on tanged spear blade. The tip of the tang is bent at a right angle and keyed to the blowgun.