The blazer is one of those wardrobe items that has all the potential to become your most worn thing. It will likely become your first-choice coat for work settings.
If you're on a thrifty mission, Helmut Lang Blazer will fit the bill. In this price range, you can also look at Set Blazer Vest. It's a popular item and won't break the bank. You might also want to consider Nicholas Blazer Vest. The price is very reasonable, but the effect on your wardrobe will be pretty fantastic.