maxxis larsen tt i got last week and used twice, now has a 10mm vertical tear in the sidewall, thanks to the welsh slate at brechfa! is it fixable or a right off?

In my impecunious youth I used to sew them back together and put a patch on the inside.

I'm with epic on this one.
Bodge it..
if you do it again maybe then its time for the bin.

its what gaffa tape was made for!!!

Sew up the hole using dental floss, big thick puncture patch on the inside and one on the outside (this is how i have successfully repaired many tubeless tyres with slashed sidewalls.