The Wallet713 (Grinbox) export-proof and verify-proof commands seem to do exactly what is required here.
I have been testing it successfully on my personal wallets.
wallet713> export-proof --file mytx.proof --id <mytxid>
proof written to mytx.proof
this file proves that [XX.XXX] grins was sent to [gAAA] from [gBBB]
outputs:
OOOOO
kernel:
KKKKKK
WARNING: this proof should only be considered valid if the kernel is actually on-chain with sufficient confirmations
please use a grin block explorer to verify this is the case. for example:
https://grinscan.net/kernel/KKKKK
wallet713> verify-proof --file mytx.proof
this file proves that [XX.XXX] grins was sent to [gAAA] from [gBBB]
<etc.>