Most people usually go for the 3.5" duals with a 2.5" inlet from Ebay, but they are price gouging them at the moment, last I looked was $300 for both. Use to be $125 for both, not sure what happened there, but they won't be selling any for that price.

2 Stainless Steel Dual Exhaust Tips Pair 2 5 3 5 Camaro Trans Am 2 5" 3 5" Low$ | eBay

With proper use of a welder and piping you could modify these to work but they are 3" inlets
2 Stainless Steel Dual Exhaust Tips Pair 3 0 3 5 Camaro Trans Am 3" 3 5" Mustang | eBay
Same thing but different size inlet $161 less.... riiiiiiiiight.