Welcome to the forum @kjetil !
Gugi’s approach with a storage subscriber will work.
Another option is to use a HTTP Transformer to send data between systems in one route.
With a HTTP Transformer combined with conditional transformer you could check if ‘manufacturer X’ exists, if yes continue with transferring the product.
If no create ‘manufacturer X’ and then transfer the product.
A request with a HTTP Transformer will not count towards the consumed tasks which is a nice benefit.
Example
This shared afas configuration has a transformer that uses the explained principle for customers: AFAS Profit [Sales Order, Customer]