You could also try using items that have high worth but aren't common currency, Gems being a big one. A few million gil might not be easy to lug around in coins, but a small bag of rubies, or even diamonds probably fetches quite the price vs space.
I tend to use Freelances method though, a signed document authorizing the withdrawal of funds to be transferred to another individual or paid out to them signed by a witness with another copy kept on my own person in case anyone tries to validate.
I tend to use Freelances method though, a signed document authorizing the withdrawal of funds to be transferred to another individual or paid out to them signed by a witness with another copy kept on my own person in case anyone tries to validate.