How can I collect customer ZIP codes at events using Shopify POS?

[stemcell]

I'm selling at an event that will give a rebate on booth fees if we provide customer ZIP codes for our transactions at the event. Using Shopify POS with Shopify Payments, is it possible to access customer zip code data? The transaction export doesn't include this info, and its probably a security measure, but I thought I'd check. 

[Figured12]

Bumping this thread to see if anyone has come up with a solution to be able to collect zip/postal codes during check out on shopify POS system. 

[Figured12]

Bumping this thread. Its been 5 years since the original question and Shopify still has not provided this tool which is the most basic thing on professional POS terminals.