"New" fuel float exploded?

[nosto]

My fuel gauge wasn't registering anything but "E". It tested good all the way back to the sender in my poly Blazer tank. Attached a variable resistor and was able to make the gauge go from 'E' to 'F' with no problem, so I knew the problem was in the sender.

Foolishly, I took another test run around the neighborhood, and, of course, I ran out of gas. So, now I have some incentive to fix the thing!

Dropped the tank and pulled the sender out. See attached pic.

Questions:
1. Anyone know what caused this result? It looks like it 'exploded'. Truck was stored outside all winter, only about 2 gallons of gas in the tank. Maybe water in the float froze??? But there wasn't any evidence of water in the gas or filters.

2. Is there a replacement for just the float, maybe plastic ? I know I can buy a new sender for $50, but there's nothing wrong with this one, 'cept the float.

Any advice is appreciated.