It’s both better and worse than that.
Because of the way bionics “pool” (for instance, technician zombies only drop a pretty short list, and regular lab bionics holders have a fairly short list to pull from), some things you’re going to get in VERY short order, relatively speaking, and then you’ll be finding dups of them forever (my late game characters will have literally dozens of most of the power generation CBMs, for instance).
Then, there’s the “butchers from scientists” stuff, and you can eventually get most of those that way (this DOES include Repair, by the way, unless it’s been changed fairly recently). Bionic soldiers seem to have an expanded list, so you can get some of the fairly rare ones from them.
And then there’s the actual RARE stuff…
Also crash sites, scientist corpses (as in, found already dead commonly with migos and/or krecks on the tile), soldier corpses (same), and spider basements (I’ve seen the strangest things in those).
But yeah, Carbon Filament is CRAZY rare and hard to get. I’ll generally have hundreds and hundreds of other bionics (not counting power) before I get that. The monofilament blade is in that category, too… not sure what else, actually. The vision ones are pretty rare, but not TOO bad, and the teleportation/quantum travel are both commonly in banks.
