Hand generate views relationship
Here are a couple of ideas for you:

1) If there aren't too many nodes with assets - you could remove the contextual filter and create an "Or" Filter Group in the regular filter section of the view (based on NID). Then just list all of the NID's you want to filter by (NID 15 Or NID 47 Or NID153). That should pull in all of the assets from each of the Nodes without having to change the view much. 

2) If you tagged the nodes containing the assets with taxonomy terms - you should also be able to use a regular taxonomy term filter instead of the contextual filter. I think in that case you would just need to add a Content: Taxonomy terms on node relationship to the view. That should open up a bunch of new taxonomy filter options in the regular filter section of views. You could then filter by term id or name.

You would just have to make sure you apply the Content: Taxonomy terms on node relationship to the term id filter when you set it up.