RTAs, generally only the glass (if so equipped) is ever going to fail. Dropsies happen, though, and it's possible to damage the 510. So multiples of your favorite. O-rings can be sourced, and the specs on those can likely be found online.
I've found that for unusual ones...the pickins' are
very slim, as far as finding replacements. Best to order that kind ASAP from a vendor.
For example, neither of the O-rings for the 24mm Berserker MTL
rta are regular, plain ones. The bottom one has a raised lip on the inside edge...to form the seal between the base and glass or Ultem tube. The top one is also an odd ball, that's thicker and has vertical sort of channels in it. On the Mini, the bottom one has the raised lip, but the top one
is regular and plain.
Only place I know that sells them, (and only as part of a spare replacement parts pack), is MyVPRO. Last I checked they were $3.99. I did find out
through trial and error (buying others on FT and elsewhere, that looked like they contained the same bottom o-rings in 24mm), that the orange and turquoise bottom o-rings from the original, old, Avocado 24, top airflow version...do work as replacements for the bottom o-ring on the 24mm Berserker. MyVPRO also
used to have them, but have been sold out for more than a year.
Avocado 24 Accessory Bag
Other Avocado spare parts bags that are available on FT and elsewhere, contain a T shaped orange tool in them and are for a
different Avocado 24 version. The o-rings
in them do not work on the 24mm Berserker.
Reason I wrote all the above - To let people know they may want to doublecheck their longterm tanks, RBA's, etc. to see if they require any odd-ball o-rings, before it's too late to get replacements.