Scratch both sides of break with 36 grit for maximum mechanical tooth. Wipe with rubbing alcohol.
Get a lightweight fiberglass less than 4 oz per square yard( the stuff sold in HD and other box stores is 8 oz or heavier). Apply 'Amazing Goop' to surface, apply round patch of fiberglass to surface and push it into the 'goop' and it should turn clear as it wicks in the 'goop'.
More than one layer of fiberglass can be used. It will remain flexible, it will be strong, it will adhere. How long it will remain that way is unknown.
Time is of the essence when saturating the fiberglass. Lower temperatures will slow the thickening of the goop, allowing more time for saturation of the fiberglass fibers. Full saturation should have the fiberglass turn transparent. but it will still be functional if the weave still shows.
I have used this method on a 5 gallon camp style sun shower whose handle ripped off. It has held for 5 months now regularly supporting 40+ pounds of hot water, upto 120F, and seeing lots of UV light.