The performance exhaust shop I used had a huge inventory of different size/shaped mandrel bent stainless steel elbows available.
they only charged me $15 for 2.5" x 10" long sections of stainless with mandrel pre-bent 45º (guessing) elbows and flared ends.
You should be able to find a shop that stocks these, try a performance exhaust shop that does good custom work...not Midas etc.
Midas will just crush bend some crappy pipe with a 90º elbow and you'll lose 20% flow rate, defeating the purpose of the Y in first place
after you cut out the factory Y with crush bends.
The Magnaflow Y (part#10778) 2.5" in , 3" out Y welded right to the 3" pipe leading to my Magnaflow (16869) CatBack kit.