You are in a similar situation as me.
Salavatski Russian #8 is your best shot.
I planted one a few years ago, but it got killed by a late frost just as it was leafing out. It did try to grow back from the roots, but petered out. I plan to try again when my finances allow, and take better care of it next time. Others here in z7a have had limited success with it.
Lyubimy (aka "Favorite") may be the next in line for cold hardiness (rumors of plants surviving in Rockville, Maryland and Falls Church, Virginia), followed by:
Surh-Anor Russian #33 (I've heard it establishes well as cold as z7b).
Nikitski Ranni Russian #19 might also work but needs further evaluation...