1 Piece Mount for .44 Carbine Rifle

[ResQ91]

Gentlemen,
Finally found my .44 Carbine and wish to install a Halo sight for close range deer hunting.
But I am unable to find a mount that fits this gun.
I was told possibly Talley or DNZ but so far no luck.
The sight requires a 1 piece rail attaching to the 2 rear screws in receiver and 2 forward screws in barrel.
Problem is the step down from the receiver to barrel.

Anyone have a suggestion for me??

Thank you for any help you may be able to provide!

[ruger66]

I think Tasco use to have a one piece mount.