PE12:82 certainly contains the old Qenya words sestainë "assimilation, imitation" and sestë "similarity".

Tama mára ké nauva, kenai er parma vanyuva enta loikarenen.. ;-)

* 'copy' is attested: quantemma 'facsimile', a complete detailed visual reproduction (by any means) of a visible thing (PE17:179)

If we could come up with a word for "unit", something like the attested erde "singularity", it could be used in such cases.

Perhaps something from √min "stand alone, stick out" "one" (of several, not alone), like GL:57's min "one single"? Though I'm not sure if that's supposed to be an adjective or a noun. Maybe ?minil or ?minit as a derivation for "unit"? But that is grasping for straws; it would be nice to have an attested Tolkienian form.

On the basis of nelesta, canasta, casta, nelta nnn. I could think of an abstraction like *eresta, *erta "1/1, unit, an undivided whole, (piece)", or maybe even of something like *usat.