There are also two versions of the SBH hammer Midway sells. One is the assembly and the other still needs the plunger/spring/pin installed.
Make sure you get the assembly if you want drop in.
Altamont offers a “slim” birdshead grip.
No firsthand experience with ‘em.
https://www.altamontco.com/pistol-grips/ruger/vaquerobirdshead/
they may be what you have pictured.