How to handle 10-digit commodity codes in Order Printer for international shipping?

We are looking at producing our own commercial invoices via Order Printer for exporting. However Shopify only supports a 6 digit commodity code. Has any one any experience of a workaround for this? Or even an app that can do the job for us? Can’t see how we can use the data from Shopify as it truncates a 10 digit code to a 6 digit code even if it’s imported or entered using Bulk Editor.