Hello,
…There’s no need for you to buy new glasses anymore, since we can take the damaged ones and get them to look and feel as they did when they were new.
The next time your glasses break, try some of these tips to fix your broken glasses before you get a new pair.
https://www.inneseyeclinic.com/2017/08/21/tips-fix-broken-glasses-get-new-pair/
I think “ones” is the pronoun for “my glasses.” However, I found many cases using “a pair” instead of “ones”. Which would you choose?
I would say ‘ones’.
‘Damaged pair’ is slightly more formal.
A pair of pants or a pair of shoes are similar.
My jeans are worn out. I need to buy new ones.
My jeans are worn out. I need to buy a new pair.
My shoes are worn out. I need to buy new ones.
My shoes are worn out. I need to buy a new pair.
My socks have holes in them. I need to buy new ones.
My socks have holes in them. I need to buy a new pair.
All of the above are OK and commonly used. Choose whichever word you want.
Thank you so much for your attention, NearlyNapping! Your sentences are really good to practice 
Both ‘a pair’ and ‘ones’ are correct.
Nouns like spectacles, pantaloons, scissors, pliers etc are always treated as plural though they serve single purposes.
Normally, otherwise, we use the singular prounoun ‘one’ as in: If the book is damaged, it will be replaced by a new one.
Compare: If the books are damaged, they will be replaced by new ones.