It sounds like the shield belonged to your character. The party cannot vote to redistribute the shield to another character, can they? Your character decides when to use it and when not to (like when he uses a 2-handed weapon or a different shield). If your character left the party, he would keep the shield, right? Then it is his asset and it's up to him to protect it.
You say your party is a "communist utopia", but even communist utopias have constitutions. So does your character possess a written document, signed by all members of your party, stating that material losses incurred while adventuring are compensated out of party treasure? Because if your character doesn't have that in writing, he cannot really establish that the party
must operate in that fashion.
I agree that it would be nice if they all chipped in to help you out. But it doesn't sound like they're required to do so.
On the "cop example": if your party were cops, you would not be allowed to keep the loot. It would not even be called "loot"; it would be called "evidence". You would have to give it to the higher authorities for storage and processing. Your party sounds more like vigilantes. Which is fine, but if Charles Bronson breaks his gun when taking out punks, he has to go out of pocket for a new one. He doesn't go shake down his fellow citizens for the money.
Moff_Tarkin said:
A life is not worth 25,000 gold. A life is worth diddly, unless you're rich or someone rich cares about you.
Is that what your Paladin thinks? Because if so, he ought to immediately lose his powers and become a Lawful Neutral Fighter in need of an Atonement and an attitude adjustment.
I do wonder why your Paladin undertook this quest in the first place. Wasn't it out of the goodness of his heart, because he is a loyal and religious person? If so, then he will surely see this loss as an opportunity to grow in holiness through self-sacrifice.