I found, only through my own experience and experimentation, that missions given in the system an engineer is located in tends to frequently give out materials and commodities required by that engineer. Especially the surface bases.
I decided to try this out after mousing over the material descriptions in the blueprints. Most of them primarily say 'given as mission rewards or found in signal sources'. Others say what kind of ship you have to find wrecked or destroy yourself to find that kind of material. So, it's not totally random.
After many tries, I'm pretty certain starting from the engineer's own system and looking for missions in the surface stations is the best place to start looking for mats for upgrading.
Also, don't dis missions that give you what you want on the basis of low monetary rewards. If you want the upgrade, only the mat is what you are looking for. Forget the money and grab the material.
I decided to try this out after mousing over the material descriptions in the blueprints. Most of them primarily say 'given as mission rewards or found in signal sources'. Others say what kind of ship you have to find wrecked or destroy yourself to find that kind of material. So, it's not totally random.
After many tries, I'm pretty certain starting from the engineer's own system and looking for missions in the surface stations is the best place to start looking for mats for upgrading.
Also, don't dis missions that give you what you want on the basis of low monetary rewards. If you want the upgrade, only the mat is what you are looking for. Forget the money and grab the material.