The nano extensions I have are metal but mine have all come out over lockdown and like you my hair is fine/thin and I really don't feel good about myself without the help of extensions.
Anyway, I ordered some tape in ones off eBay. Omg, I love them. I guessed at the colour I thought looked the closest and it's an absolute perfect match. I got a pack of 10 but I've only used 1 each side and I'm so pleased.
If my hairdresser wasn't a good friend I'd definitely not have the rings again. I'm going to discuss the tape ins with her as obviously professsional insertion would be better.
The hair on the ones I got is real hair, they came in 2 days and they were £15 !!!! Literally stick a 2" strip either side of your own hair, like a sandwich. They wash and dry lovely too.
Worth a look for the price