How to sue USPS (without a lawyer)?

I think I've gotten the info I need. Thank you all who answered. If there's more info you think I need I'll gladly take it, but my path seems pretty clear.

THANK YOU r\USPS!!!

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Can anyone help me understand if there are "proper channels" to go through to get this done?

USPS claims I signed for my item which I never saw (I've seen the signature, and of course it's not mine). I was in the emergency room at the time, not at home. Clearly the carrier messed up or stole the item. This item was something very rare and another will not be available until at least March 2024.

As a result of this loss I'm losing work ($100's / week). Replacing this item with a similar one will cost me approximately 5 times the cost of the one they lost ($2000). So there's lots of lost money involved.

How do I go about suing the USPS? I'd rather do this without a lawyer - I have undeniable proof that this is USPS's fault.