Method to append USPS Tracking w/o using Shopify Shipping Labels?

[Scott_Booher]

I have a vintage stamp business serving the wedding industry, and therefore it's important that I use actual USPS stamps on the shipping envelope to customers, rather than a computer generated shipping label/postage.  The USPS has recently begun phasing out the use of tracking stickers which were available for free at each post office - and could be appended to envelopes carrying sufficient postage.  Does anyone know of a solution which would generate USPS tracking info/labels, while allowing me to continue using USPS postage stamps for the postage itself?  Many thanks.