To unlock the white and black swimsuits for Lara you must complete the game, find all the rewards (including the ones in Croft Manor) then complete the game again under the time trial difficulty. Complete Bolivia Redux in time trial mode. This will allow the use of the "One Shot Kill" cheat which will help significantly. Note: This will also unlock everything else in the game, including the pistol upgrades, another thirty costumes, and the "Wield Excalibur and "Wield Soul Reaver sword" cheats.