Leather pen cases.
Individual (i have both soft and hard leather individual pen cases).
Double (one of those where each of the two are kept separate of the other.
Oh, and two leather smartphone cases of the pocket kind I found cheap on a sale. Here they are all banging against each other so I use them for the briefcase where they'll not be too loose.
You can find cigar boxes shaped to keep cigars separate that will work as well for pens.
Ah! I forgot: I also have a couple of lens cases (you know, for reading lenses) that are slim enough, metallic for endurance, soft lined on the inside, and where I can safely carry two or three pens as well as a microfibre cloth to protect/clean/polish them and -occasionally- I carried an insulin (1ml) syringe and small vial for refilling.
In other words, there are way too many cheap methods to keep your pens safe.
Ah, yes! And I also have a small metallic Berkleys mints box that I use to protect a tiny weeny mini "Peggy" pen. Like their larger, standard sized Altoids or Berkleys boxes, they are great safe EDC carriers (that's where I keep nibs, and you can use their different colors to code contents).
And for some, like others do, on a shirt or jeans pocket (love that with the Montblanc Noblesse) --so, draw off three points from my score!