Of the three, Adams would seem to make the most sense. Bell is obviously the best of the three, but he's due to be a free agent and would likely take a notable minor league player to acquire. Mike Adams, on the other hand, is under team control until 2012. The righty has had a fantastic year so far pitching to a 1.32 ERA and 0.71 WHIP through 41 innings. That said, given that he's controlled for another season, the Padres may be less willing to give up him right now than they would Bell, who is all but certain to leave after this season.
The other possibility is 32 year old righty Chad Qualls, who has also been strong this year with a 2.60 ERA in 45 appearances. Qualls is only making $1.5 million this year with a club option for next season.
Baseball's non-waiver trade deadline is July 31st.