Ah! now we know the application so advice based on experience can be given. Having used many 385 motors and some in submarines, I’m happy to use a short length of silicone fuel tubing. Provided it is a good push fit onto both shafts then it works well. You do need to get the shafts in line to minimise any power losses.
It’s silent, durable and, best of all, cheap.
GlynnGuest