I'm not in your climate so I cannot help you with that.
Not sure why you are so set against a tree grown from a seed. To me, there are three options.
The best of all worlds is probably a tree produced by a cutting from a known cultivar. I don't know how easy these are to find. I suspect most cultivars are grafted, not rooted from a cutting. I don't know this, just suspect this.
A tree started from a seed will still probably produce pretty well. Maybe not as well as a known cultivar, but maybe it won't be all that disappointing. Nuts are not quite the same as fruits as far as growing from seed. The advantage to growing from a seed is, if the tree dies back to the ground, it will likely come back from the roots. This tree would have the same genetics as the seed. That is a big advantage of a "cutting" too, if you can find one.
A third option is a graft of a cultivar onto a rootstock. If the rootstock is selected properly, it may give you a more vigorous, disease resistant, hardier tree. The disadvantage is if it dies back, whatever sprouts from below the graft is rootstock, not the cultivar you want. Another potential problem with a grafted Carpathian walnut could be that sometimes black walnuts are used as rootstock. My grafted English Walnut I got from Stark Brothers is. A black walnut rootstock will produce juglone, which inhibits or kills some other things that try to grow around it.
The main reason I responded to this post was to mention the risk from the juglone if you get a grafted tree. You need to find out if the rootstock is a black walnut. It may not be. If you are not familiar with this risk, Google "black walnut juglone" and read up on it.
