Adapter for a dovetail?

I have a Golden State Arms No.4 Mk.1, it's a nice "civilianized" job (Santa Fe model 1944)
The rear sight is an Express type in a transverse dovetail.
I need something easier on the eye than the iron sights.
What would be perfect is a transverse dovetail to picatinny adapter and a small RDS.
Every search I try for "dovetail to picatinny adapter" gives results for longitudinal dovetails.
The nearest I can find to what is needed is the Volquartsen Dovetail Picatinny Rail Mount for Ruger pistols, but the dovetail is too wide at 0.546".
My dovetail is 0.375" wide.
Anyone know of a suitable adapter?
Thanks, all.