(How to) Link to Publisher Version without DOI?

This publication has no DOI and thus I can currently only add links on the webpage for preprint, presentation, and supplementary webpage. Is there a nice way (except annote) to link to the publisher's version as well?

The publication does have a URN using its National Bibliography Number, which can be resolved using https://nbn-resolving.org/, so one possibility would be to allow specifying a URN as alternative to a DOI. But I would also be fine with just providing a link to the publisher.