where can i buy a flange for a dump tube for my wastegate?

 

Ebay

 

my guess is you have a Tial 35/38 mm gate, or a Delta gate (very common gates) and they actually use the same inlet flange as they do as the outlet flange. So you can get them at just about any online flange shop,

www.roadraceengineering.com
www.cheapturbo.com

 

turbonetics evolution wastegate actually but its 35 mm, thanks ill check those out