I try as much as possible to support the little guys. That said I've had good luck with local saddle makers, they generally are happy to make exactly what you want and for them those little bits of leather are mostly scrap so prices are generally very reasonable. Outside of the saddle makers there is only one dedicated gun leather guy I whole heartedly recommend and that's Rob Leahy at Simply Rugged Holsters.

https://www.simplyrugged.com/