I have been looking a lot for some information about the topic. I know for sure that zombie villager spawners are technically possible to exist in Minecraft. So I wonder if that kind of spawner can be spawed naturally. After some search on the internet I could not find anything about it. The only thing that I came across was that a zombie spawner has some % chance to spawn a zombie villager. So after a lot of brainstorming and testing/looking, I still have no idea if this is possible.
There doesn't seem to be a way for zombie villager spawners to occur naturally. According to the official wiki, there are only spawners for:
- Zombies (dungeon).
- Skeletons (dungeon)
- Spiders (dungeon, woodland mansion)
- Cave spiders (mineshaft)
- Silverfish (stronghold)
- Blaze (nether fortress)
- Magma cube (bastion remnants)
And by the way, only the zombie spawners in Bedrock Edition occasionally spawns zombie villagers. Java edition zombie spawners stopped doing that in version 1.11 when they converted zombie villagers into a completely separate mob instead of just a cosmetic variant of the generic zombie mob.
The only way to get a zombie villager spawner in survival mode is by cheating. If cheats are enabled in your world, you can use the command
/give @s zombie_villager_spawn_egg to obtain a zombie villager spawn egg, which you can then use on any spawner to convert it into a zombie villager spawner.