You might find someone who has recently replaced his shocks and now wants to change them again to track the car, but I would suggest against putting old shocks on. Most of us wait way too long to replace our shocks, so you would not be gaining much.
I have been a fan of Koni shocks since the first set I bought in 1972, but on a 13-year-old commuter car, I would go with Sachs, which a a bit cheaper and are OEM.
You are sure that the problem is the suspension? The convertible has a vibration dampener in the trunk. Are you sure that someone did not disable that so they could put in a cheaper battery?
To limit your costs, another option would be to buy new Monroe shocks - $40 ea for rear, $90ea for front on RockAuto. I've not tried them and they are clearly not OEM, but should be better than your old ones.