side exit exhaust

Dynomax Super Turbo Mufflers 17675
Edit: went back to check price....disco'd.

$140ish
SpinTech Sportsman Splitcase Muffler
Looks like this is the Mustang crowd's overwhelming choice.

$130ish
Flowmaster 80 Series Crossflow Mufflers 842580

If it was me, I'd go to the smallest, greasiest, sootiest exhaust shop in town, and ask them. FWIW, 'inexpensive' is a relative term.