How to Fix Eschew Materials

[MaxiDuRaritry]

Doesn't work. Eschew Materials only allows you to ignore material components. The tuning fork is a focus component.

Also, the tuning fork doesn't need to be made from something from the target plane. It just needs to be "A small, forked metal rod. The size and metal type dictates to which plane of existence or alternate dimension the spell sends the affected creatures." What metal corresponds to what plane is left to the DM, so that they have control over how easy or difficult it is to get the right tuning fork.

After looking things over, you're correct.

Though the same still applies for simulacrum and ice assassin.