#029 entry in bootypedia covers the ways of raising bravery: use medikits, pilot ships, go in combat naked (or almost naked).
For aqua plastics: rob\enslave armored guys (trader security, osiron people, etc.), or go raid a Sunken USO for hundreds of 'em. Purchase is locked behind "Prize: Military Supplies". Actually, you will need a fair amount, because you'll need plastics for heavy armor -> defender armor -> guardian suits, which are pretty solid mid-game armor, and some other things.