Are there proscriptions in AL to prevent a transmuter wizard from owning multiple transmuter's stones? The idea is to keep the ones producted by his simulacra and keeping them also in different modules. Is this allowed?
I read through the Adventurers League Players Guide v9.1 and the Adventurers League FAQ v9.0, and I could not find a rule preventing this.
It appears that you could get arbitrarily many transmuter's stones in this way. Initially you would be limited by the material component cost of 1500gp per simulacrum spell, but once your simulacra get wish you can remove that limitation. These related questions have more details:
What happens to a wizard's transmuter's stone when she dies? (answer is it still exists)
Adventurers League has rules about trading magic items, but the transmuter's stone does not appear to be a magic item per that definition. (If it were a magic item, transmuter wizards would have to count it as part of their own magic item limit, which seems unfair.)
Adventurers League also has rules about simulacrums (preventing you from exploits involving wish or chained simulacrum) but this specific exploit is not prohibited.
However, please note that the Adventurers League DM has Rule 0 authority over what happens at their table. It's likely that many Adventurers League DMs would consider your plan to be an abuse and would tell you that it's forbidden at their table, even though there's no official rule against it.