Has anyone ever figured out a clever way to screw on a  typical universal aftermarket rear turn signal on a 2005 s40 Boulevard? Or am I stuck getting the expensive OEM part.

I can't speak for any other Savage, but the 2005 turn signal stem is a metal bar held on by a screw perpendicular to the bar through the bike's pinion. The universal aftermarket signals just screw on directly and are held in place by a washer and nut.

I'm surprised so little info is available on these things online. I bought a pair of aftermarket  tail lights ovee a month ago and now I can't refund them. They were apparently compatible with the Savage... but this doesnt seem to apply to my model. The screw on stem makes it seem impossible to attach without an adapter of some kind (which doesn't seem to exist!).

These are the turn signals I bought:
https://a.co/d/4YimIIX

On the picture I attached, the OEM stem is on the left and the aftermarket screw-on stem is on the right. Is there any hardware solution, any adapter to make the aftearket one work, or do I just have a wasted part on my hands?