The door boxes have pins on the top that locate in holes in the bottom of the door handle
The only fixings in the speaker covers are screws at the bottom
Having had quite a bit of success repairing my cracked door boxes I think the pins could be recast if needed
The door boxes / speaker covers are made of ABS/GF which is a type of plastic (now I feel like Im telling my grandma how to suck eggs) but anyway
The good part about ABS is that it can be melted with out any loss to its molecular structure, so in the case of casting new bits or repairs you only need a few simple things
A glass jar or small glass container the can be sealed air tight
A pile of Lego bricks of you color choice, I normally use black
A bottle of pure 100% Acetone, not nail polish remover
And a bit of skill and lateral thinking
Place a few Lego bricks in the glass container, now add a glug of acetone, seal the jar
After a while you will notice that the bricks are starting to melt to get the consistency you need for your repair either add bricks or acetone
Lego bricks are also ABS, so when you add your melted bricks to your repair they all melt together and as the Acetone evaporates the ABS returns to its original structure, so a perfect repair with no joins or glue
