Item labels are a bit of a pain in the a%$. Limited fields are exposed.
Previously for a client I built something off an item receipt to print labels based on the lines on the IR.
In the case where you have items that might be big numbers, I added a custom field on the item (and default this to the IR line) for "Print 1 Label per ?? Quantity".
I then created an IR search to generate the list and built an Advanced PDF of that search.
Then find the link to generate the PDF (usually in your downloaded files) and add an INLINE HTML link which substitutes the transaction ID into the generated link.