Integer ID sequence collection in a cluster environment

I need an integer id field, but I also left the ObjectId.
I followed some examples and created a sequence collection with an incrementing field for each collection I need it for. The fields are incremented by the C# application.
The problem with this solution shows up in cluster environment, because (as far as I know) it takes some time to replicate the product_id++ to other nodes in Mongo cluster. In that case there could be collisions in product_id depending on the Mongo instance access pattern.

Any way around it?