I just went through this Monday and ended up getting some 2" schedule 40 aluminum. It fits right inside the TBM outlet with a little space for some 5200. This isn't the perfect solution because of the thickness of sch 40 (1/8"+) and it's just not needed, however, it's readily available and cheap.
You are looking for tubing that is about 2.38" OD, and the stock tube is only about .049" thick, so sch 40 has an ID of 2.07" and the ID of the stock tube is about 2.25"
So, yes, sch 40 works, it's just not perfect and adds about 2lbs over what the ideal application would be.
Steve