$6.99 for a steel one isnīt that much cheaper, considered shipping expenses it might come cheaper to order a complete Vamo V2 from Fasttech or Vaporbreak.
But your idea of replacing one top cap with another got me to think ..... isnīt there some other mod, maybe a cheap mechanical one for which the top cap is available separately with the same diameter?
I.e. I own a Lambo 6.0 which has the precise same diameter as the Vamo, even the extension caps fit into the screws.
It has a screwed top cap, and the cap isnīt available separate, but taking this as an example I assume there should be plenty of other mods with the same diameter and at least for some of them the top cap should be available.
If only I knew which ones fit.