76 bonnie battery dies quick, need to replace trim too

Hi - I am not a weekend mechanic or anything; I live in new york city, and my beautiful 76 bonneville (4 door, 400ci, 45,000 miles) is my first car, so please keep this in mind with any replies...My problem is my battery keeps dying awful quick - At first it was a hot start problem, which one guttersnake mechanic didn't fix (but did rip me off substantially) by replacing the battery and alternator a year ago. A second, trustworthy mechanic said it was a timing belt problem, and that did fix it.
But Christmas eve, I got clipped by a cab driver, and while waiting 15 minutes for the cops with the engine off and lights and wipers on, the battery died. Can I get a more powerful battery, or should I buy a battery recharger or something. Also, the boat is missing some wheel-well and side trim, anyone know where I can get something that I can bend to the right shape, or should I give up?

Thanks,