Leviton offers a Label Kit for the e2XHD system, part# E2XHD-LBL. This kit takes the place of one of the cassette positions within the panel and provides a label holder. The kit includes 4 label holders and corresponding designation cards and designation windows.
Another option that does not use a cassette position is to use a Brother label machine paired with 3.5mm tape. Tape part# TZe-N201 (Brother Super Narrow Tape). This tape is narrow enough to be placed over the port numbering on the e2XHD panels.