70-300G would probably do the job. It's a shame you couldn't get one from the vast circuit city closeouts that were going for $500 or so on average... a very excellent deal at that price.
Of course there is the new 70-400G which is absolutely fantastic (and I hope to acquire soon). At $1500 it is quite spendy though.
The South Coast Plaza sony store has every lens (even the 300 f/2.8 G). Bring your a200 and try them out there.
There's also the third party route but any telephoto of decent quality gets up there in price unfortunately...
You could also find an old 70-210 f/4 (maybe too short) or the 75-300 f/4-5.6 (old style), commonly referred to as the Beercan and Big Beercan respectively. They both look alike, the difference is that the 75-300 has a focus limiter switch. You can find these used for reasonable prices ($2-300 for mint copies) and they have excellent IQ.
[Edited 2009-03-16 19:01:54]
[Edited 2009-03-16 19:02:33]