The OP should simply buy a 1-1/8" x90mm stem with the right angle and clamp. There's a decent selection still available with 26mm clamps including NOS Thomsons, and on down to some generic types. I have both Thomsons and Oval Concepts available NOS, but they're kind of pricy for what the OP probably needs to spend. There are plenty of 26mm stems out there.
Stem shims are readily available and work fine.
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