Take a look at the MDD, Annex II or Annex V, Section 3.1 on Quality Systems:
3. Quality system
3.1. The manufacturer must lodge an application for assessment of his quality
system with a notified body.
The application must include:
.
.
.
— a written declaration that no application has been lodged with any other
notified body for the same product-related quality system,
So, as I read this, if the nebulizers were made using different quality systems, you could have 2 notified bodies, however if they are made using one quality system, you can only have one notified body.