Maintenance What size elastic to use for Zuzu Delf?

I think 2mm work. Unfortunately I haven't restrung any of my zuzu's but if you you check the fabric section, you can get round cord elastic that you can buy in a pack or by the yard. Just bring your old elastic to get as close to what your doll originally has. You can also find elastic on Etsy but it's better to find in a store even at Walmart so you don't have to pay for shipping.
https://www.joann.com/round-cord-elastic-50-yds-white/7705122.html

 

I was recommended to buy shock cord from a paracord supply shop, and I will never go back to the stuff at the craft store. It has great tension.
I bought mine from an online shop called West Coast Paracord but you may be able to find a similar store closer to your area. For that shop in particular, the smallest shock cord they have is 2.5mm, not sure if that is too big for your Zuzu Delfs and other tinies.