Installment Plan

Story, first published: Galaxy Science Fiction, Feb. 1959

Positronic brain plug-ins, or "transmogs" (from a curious english word "transmogrify") - robots have learned to reproduce by assembling more of themselves from spare parts.

Abrams, Avi: Science Fiction and Fantasy Reading Experience: Clifford D. Simak

A work gang shows up on a remote planet to collect the harvest of podars needed for medicine, but the natives won't sell.

Wikipedia: Clifford D. Simak