Ronny, yes getting tires or a lot of other parts for the P 133 is getting hard. I have 4 P's so I know all to well. Have you seen a Ninebot E yet? They're the China company that now owns Segway. The Ninebot has 16" tires. The tires are made by Michelin I think. They do look a little wider though. If there's a Ninebot dealer close to where you're at stop by and see if you think they might work. I know the rims are different but a good bike shop could change the tires on to your Segway rims. Here's a link to Ninebot's US distributor listing their replacement tires and rims. Good luck!
http://www.ninebotus.com/tire-assemb...nebot-e-elite/