Signature required upon delivery?

Hello all, 

A recent client of mine has messaged me asking, "Hey, we sold a lighter on the new website!!! Only issue is I cannot figure out how to add signature required to the shipping."

I contacted Squarespace to figure out how to add this delivery option, but was told, ""It's not currently possible to require a signature within shipping options, but I'd be happy to suggest this to our development team to review as they continue to expand the platform's capabilities."

I'd love to know if any of you can recommend a workaround or a third-party extension so we can require signatures upon delivery of each package.

Thank you so much!