honestly, you seem a little obsessive about this. Most people would not think it worth this much trouble... Is it the thrill of having something so universally hated and somewhat "dangerous," that no one else plants? There's something going on here that I don't really understand.... It isn't about being able to eat the plant or use the mile a minute some how, because there are MANY more edible plants/ weeds (I understand that kudzu isn't really edible in terms of being able to get it down, unless you juice it like wheat grass) and useful plants/ weeds, that would not require trying to keep it under guard, nor risk having your house engulfed and everyone hate you.
(In case you think I am kidding:)
You can't get them in catalogs, because illegal to sell.
There was an interesting set of instructions once in Mother Earth News Magazine:
"Plant at night so neighbors won't see you and throw rocks,
Drop seed and back away quickly. DO NOT HOLD IN HAND.
Fertilize heavily with cinder blocks."
I found one place that sells kudzu vine seeds: https://www.chilternseeds.co.uk/search?q=Kudzu+vine
but they are in the UK. I imagine it would be illegal for them to sell/ ship to you.
But really it is not hard. If you are so obsessed with this, find a roadside with kudzu and clip yourself some. It often appears on sites that have been disturbed - road cuts, logging areas, etc....