If not, I'd say to go forth and ask around on the various moped forums, like Moped Army and what have you. (You might ask there anyway, as there may be a specific reason it's best to use the original size tire)
Thanks for the tips, but the Chen Shin only went up to 17" diameter. The other sites had nothing either. Maybe with the resurgence of the mopeds, someone will make a vintage tire to fit. We can only hope.
The 23 in your tire size most likely refers to the inflated diameter, similar to the way bike tire sizes are designated. Current motorcycle/scooters give the rim size, tire width, and aspect ratio. I think you might have 18" rims
the 16" to 20" motorcycle to bike tire thing works because the rims are 405 and 406 milimeters. I forget which is which. American Bikes measure the inflated size, Motorcycles measure the rim size, and the french had there own system that i fail to understand. Lucky my Peugeo 103 was sold as a motorbike, so it uses motorcycle standards and 17 inch rims. your Mobylette i think was sold as a bike with Motor, and the rims could be based on bike sizes. Crazy French.
MopedArmy.com is the first place to ask. Sheldenbrown's website explains the sizing some