I have a pair of Blackfin Costas and before I get crazy with the super glue I figured I'd ask the professionals on the outdoors board the best way to fix these bad boys.
They are prescription and old so Costa was a warranty"NO"

Costa has replaced two pair of mine when that's happened

Same here.

Send them in. I sent my 5 year old fantails in a few months ago and got an upgrade from 580p to 580g when I got them back!

2 pair of Tuna Alley with the same issue got fixed for me under warranty. Did you send them in and they said no? Usually with Costa you send them in first

Yeah I don't know if any adhesive that will bond with that material. Send em in.

You could try gorilla glue. The clear gel.

You will have to apply dots along the way with a toothpick. Then use toothpick to spread evenly.

Either that or send them back.

I tried super glue to marginal success. then sent them in. They fixed them but said using glue should have invalidated my warranty.

One more vote for send em back in. They replaced mine with a new pair

Mine did the same thing and were fixed under warranty. Send em in.

Were all of y'all's prescriptions as well? I've not wanted to send my prescription glasses in for the same reason. I thought the prescription warranty was for like only 2 years. My rubber nose piece also came unglued

I've sent a pair with the same issue. They just took my lens out and put them in a new frame. Super easy.

send them back, I got a new pair when that happened as well

I sent mine in when that happened and they sent me a new pair

They don't have a repair department at the moment because of COVID.
I ended up getting a replacement pair and I need to just pop my prescription lenses in the new frames.
They DO NOT cover frames on prescription lenses
The reason I'm now asking about an adhesive for these frames is I'm keeping them and I'm curious if anyone has had success gluing the hydralite back to the frames

Never seen a "premium" brand with as many *****es, complaints, and lack of warranty service as I do with Costa.

Would never own a pair after observing.