How long have you been feeding raw? What varieties of protein have your ferrets accepted with soup (if any)? For any they've accepted, you may be able to finely sliver pieces and try it out. Mine were young when transitioned so I skipped the soup phase, but I'm sure there will be lots of advice incoming!
1# Put the switch on hold until you can reorder a blender or 2# Go full manual. (Make the soup entirely my hand, using a cleaver)
Trust me I did this. I do this for organs since I still have no blender. The only issue would be it will not go to the same consistency. It will be little chunky rather than smooth, but it can be done if you're desperate.
3# Go straight to slivers and hand feed. If you have a young ferret, this one would be the best course of action.
If you happen to have a baby food maker (read: teeny tiny food processor) then that would work for up to 5 ounces of food per blend! That's what I do for their organs so I make sure they eat the same amount.