https://www.walkerexhaust.com/content/dam/marketing/North-America/walker-exhaust/pdfs/Walker Elbows.pdf
https://www.dynomax.com/downloads/product-catalog/2015_dynomax_customfabrication_secure.pdf
The OP is asking for an I.D. to I.D. elbow.
The above links have I.D to O.D. elbows, where only...