I'd recommend the Gold Tone Bob Carlin open-backs, both of which I carry.
1-3/8" nut.
BC-350
https://www.banjocrazy.com/5-String_Openback/BC-350
CC-Carlin12
https://www.banjocrazy.com/5-String_...-Cripple-Creek
I play a BC-350+ which is a discontinued version of the BC-350.
Here I'm using a skin head.