To unlock the Bandana and Stealth Suit easier, wait until Act 5 (Drebin's prices are 50% off) to get the items for 2.5 million Drebin Points each instead of the 5 million Drebin Points they normally each cost.

--NOTE--
this is only if you are playing the game again using the same save, it will not work during the first playthrough as they are not available, plus you will have more drebin points.