Replicating a silicone object
I agree with #torjek that a separator (mold-release) spray or liquid would make it possible to caste a silicone object with silicone as the mold making material.  The benefit of getting good at this technique is that you could then caste replacement silicone earplugs using the mold which you just made out of silicone.  

If you need more protection for your original, you could probably cover the original with tin foil, using embossing tools to smooth the foil into all the nooks and crannies, and maybe some modelling clay to smooth out the foil seams. Once the original was completely protected within its foil armor, it could be caste as normal.

You might also want to search the term "silicone on silicone casting" on youtube. There seem to be a few mold release products which can handle that requirement. Not sure that any of them are safe for your expensive original. 

Have you considered self-hardening clay for the first mold?