Original tires are non-existant. I actually did some research on this site to find a replacement.
5.30x4.50-6 is a utility tire for garden carts or something. But they’re a perfect replacement They have a street tread pattern, and fit under the fenders great. I think I paid $40 for a pair on eBay. They’re not speed rated but the bike only does about 30 so speed rating isn’t really a concern.
I’ve been riding it around and havnt noticed any issues.