How to find someone to (once) pick up and re-send an envelope in Cancun? [closed]

Last week I went to a Fedex office in Cancun and sent an envelope to the US. Unfortunately a few days later I learned that the package was returned to the same Fedex office because a small amount of cash was in the envelope.

I am now in the US and cannot currently travel to Cancun to pick up the envelope. However, Fedex told me they would be able to give it to someone else if they show a power of attorney signed by me.

My question is: How can I find a trustworthy person in Cancun to (1) go to the Fedex office, (2) show them the power of attorney and obtain the envelope, (3) open the package and remove the cash, and (4) send the rest of the contents (some papers and an ID card) to me?

Of course I'd be willing to pay for this. For obvious reasons I'd prefer someone associated with a local entity as opposed to a random person off the internet. I asked a few local hotels, but no luck so far.