Does anyone know where to find a 2.5" or 3" downpipe... to replace the GReddy downpipe from a GReddy GSR turbo kit?

I'm planning on getting the 'car sound' 3" cat and Thermal 3" exhaust... and with all these (free flowing) modifications to GReddy Turbo kit, will I be running lean or will I encounter any other other problems?

Here is my application: 1999 Acura Integra GSR (3-door) w/ GReddy Turbo Kit (TD05-18G) and GReddy Type24 FMIC.

 

Prolly at your nearest local exhaust fabricater.