I had to add the D-Rings to my HA-114, which was very easy. You can also get the "official" Hohner strap hardware, which does look better (I think Claude was suggesting this recently).
I do NOT recommend the clip-on luggage strap approach because the clips end up scratching the accordion. Instead, get a real accordion strap.
I have purchased the D-ring hardware kits from Larry
Miller .. But I do not know if he still provides
parts, since he has retired from making accordions.