Maybe you're just looking for stainless in all the wrong places. Here's what I'd do in your situation: Check out the cost for an aluminized or carbon steel replacement exhaust (like the local shops probably stock). Buy or borrow one. You don't need it for long; it's just a pattern.
Find your stainless pipe/tubing from ebay or a local steel supplier. You want a 300 series stainless; 304, 312, 316, 316L, etc. (400 series will rust). Take your pattern and materials and find a local steel fabricator with a mandrel bender (anybody fabricate roll cages for race cars in California)?
Don't be afraid to think outside the box!
When it comes to welding the stainless, stay with a filler wire which begins with a 3. You want 308, 310, 316, 316L. Maybe ask your local welding supply for advice. Stay away from 309. 309 is used to join stainless to carbon steel and it will rust.
http://www.weldingwire.com/Images/Interior/documentlibrary/stainless selector guide.pdf
Now you need a muffler shop that can weld stainless. Good luck with that. You might need to bring them a roll or two of stainless wire from the weld supplier. Ask them what size wire they're running and offerr to buy them some in stainless. Tell them they can keep using the Argon they're already using for shielding gas. See pages 28-30 here for some starting parameters:
http://www.lincolnelectric.com/assets/gl...316L/c64000.pdf
GMAW welding is the process that muffler shops use. This is semi-automatic wire feeding; and satisfactory results can be obtained at a reasonable cost.
GTAW is more expensive, usually called TIG welding; this requires a higher skill level (both hands must be used), it also produces higher quality welds. The fellow listed above who paid $1200 for a 1991 Buick exhaust either had TIG welds or he was ripped off. Any shop capable of this will boast of it. GTAW welding holds together NASCAR roll cages, high quality racing headers, coal and nuclear fired power plants, yes, the space shuttle, etc.
Good Luck! I'm probably 1600 miles from you, but I'm a semi-retired boilermaker and welding supervisor, don't hesitate to PM me if you have questions.