I'd target Garza if you can. Maybe try Rivera first. I think Lee can only get better with Aram back in the lineup.
I'd def try and buy low on Hamels. As a frustraded Hamels owner, it's getting to the tipping point.
Note this, if the original Hamels owner still has him, he may believe in him still (like I do) and want high value (Lee + Rivera) or 1 of your better OF. If he's swapped hands, aim low.
AJ Burnett might be reachable. As trade banter, you can talk about his high whip (which'll prolly stay high). However, he's had some brilliant outings so that might also be hard. It's definitely a sellers market in pitching right now as nearly all the top starters are performing very well. The ones who struggled before are doing better.
Maybe try to buy C. Lee? He hasn't been doing well and Cle ain't gonna win him many games. Maybe could get C.lee for D.lee.
Plenty of options. Good luck (maybe also post your current pitching staff).