Pets are kind of my thing in MMOs. Istaria has them too, but for the most part they were all from events, and I do not think that there is even a single one available to anyone in current day Istaria unless they can find someone who got them a long time ago.
This, despite the fact that there are 31 textures meant for shoulder pets that I can find in the game files. So, I propose that at least some of these shoulder pets be added to loot tables as very rare drops. A few could also be added to the proposed soul shard vendor.
Ideally, some of the ones that have mob counterparts would drop off of those mobs, e.g., a maggot pet dropped by maggots or a wolf pet dropped by wolves, and shoulder pets would be spread across all six tiers so that even lower-level players have a chance at getting some (and possibly then selling it to a higher-level player because shoulder pets are not really tied to tier with regards to who wants one).
I would see these being attune-on-equip and not attune-on-loot, at least in general cases.
I also would implore the devs to make any of these shoulder pets usable by dragons as well as bipeds rather than only bipeds as has been the case in the past with the exception of maybe two.