you can always make an invoice and copy it and give it to someone in physical form, on a usb stick or printed as a QR code

but that's an invoice, the signed payment is a payment (payment request, actual payment)

lightning payments in this payer-initiated format are called "keysend" or "AMP" and have to be submitted to the payer's lightning node to work, meaning access to the LN RPC, which is not the usual situation for a lightning node (usually access to that RPC is private to the person using it, for security reasons).