The Russian steppes have a ton of rivers actually, so you can still preserve your initial plans if you want, you just need to consider a river or two. If they are flowing north you may also want to consider a large frigid delta at the end - if you're looking for real world inspiration I'd suggest looking the Ob River, the Lena River, and the (Canadian) MacKenzie River.

An arctic and near-arctic delta also mean you can include pingos!