I got mine at electricscooterparts.com a few years back, they no longer have them in stock. The first time I saw them on a Bladez 300 electric scooter, I knew I had to find me some, I think I have the last two NOS sets in existence. I have seen them listed on a German scooter site but never ventured further than the search query. They weren't cheap ( $25 a tire ) and they use a 9x3.50-4 tube which wasn't included. The picture is of the tire on the rim without being inflated, they do round off a bit once inflated but they are still the lowest profile 4" tire I could find. I have two sets NOS, I'll ponder letting a set go seeing how I haven't used either set.
A2M