Teleconverters

[Tindomul]

So I was thinking on getting a Teleconverter to increase the zoom on my lens.
I have a Nikon D40 with a 55-200 mm lens. What Teleconverter would you choose if you are on a budget (wanting to spend no more that $200 unless its really really worth it, then I will go as high as $250).
I like to take pics of little warblers, and those birds are so small and usually so far away most of my pics are super blurry when I get home to check them. Very frustrating.
Thanks.