You probably need to use an actual plumbing supply house.

You can look around Genova to see if the part is even in the catalog.

Here is a link that might be useful: Genova PVC

found this

More stuff here.

Lasco fittings

This page looks like it might exactly what you want. 3x3 with side inlet in 1.5 and 2"

Lasco Page 281

Link is wrong

Lasco Page 281

Link still not working right. Google it.

The fitting that Joed ed has posted above is a 3x3x2 low heel inlet closet bend, but it is upside down in the illustration.

They also make side inlet closet bends that are configured like the fitting your looking for but I don't beleive they make it in 2".

Also be very careful. That is a specialty fitting at it is very limited were it can be used.

Perhaps if you could tell us what your trying to hook up we can help you find a solution

the venting for my shower, i have to run it up the wall and tie it into the main vent stack, the stack is 3 inch and the shower vent will be 2 inch. i could just use a tee but i thought its be easier if they just made a fitting like this.

Code prohibits running a horizontal vent under the floor. A vent must rise vertically until it reaches an elevation 6" higher than the flood level rim of the tallest fixture served by that vent.