Fair enough. I would follow ranochigo's advice above about using coinb.in instead then. Alternatively, if you are familiar with a light wallet such as Electrum, you could export the private key(s) of the address(es) you spent coins from in the first transaction, import that/those private key(s) to the light wallet, and use it to create, sign, and broadcast a new transaction.

You would need to use the command dumpprivkey "address".

See here for more info: https://bitcoincore.org/en/doc/0.21.0/rpc/wallet/dumpprivkey/