An OEM equivalent resonator shouldn't break the bank and it is by far the best solution. Google "Walker OEM exhaust" and search their catalog for the part number.

A cherry bomb muffler uses spun fiberglass over a resonated inner tube. They don't do a good job of sound deadening to start and they won't last nearly as long an OEM equivalent resonator. Even if you go to the trouble of making a cherry bomb fit, you will be back to square one in a year or two once the fiberglass packing has sooted up or blown out.

Unless the car is weeks away from being sold or scrapped, I would buy a OEM resonator over the counter. To mount it, trim the ends of the OEM exhaust tubing and use slip-fit connectors and U-clamps to attach the new resonator. That way, you shouldn't have to bother with any welding.