Short answer: There isn’t a single fixed number. Shwetambar Murtipujak comprises several gachchas/sub-sects, and each gachcha has its own Acharya. So, the total count of Acharyas varies by lineage and tradition within Shwetambar Murtipujak. For example, different sub-sects like the Tapa gachchh have multiple Acharyas, and other Shwetambar lines also appoint their own leaders. If you tell me a specific gachcha or lineage, I can name the current Acharyā for that tradition. You can read more about the general question of how many Acharyas there are here and here.