The requested text seems not to be available there.
I have on my computer a file for Thirteen Principal Upaniṣads, including the requested text, typed by the late Muneo Tokunaga in 1989.
It contains the phrase "The copyright of this text belongs to M.T. Duplication of the text allowed only under agreement." But since he has generously made public so many other e-texts, I suppose he wouldn't have minded this one being shared. So here it is.
The transcription scheme has not yet been normalized but I am sure some clever colleague can help with this.
May I go off topic and ask if anyone knows whether there is any hope that GRETIL can become active again, or whether some alternative cumulative repository can be set up? Olliver Hellwig's recent announcement of an e-text on his own github platform shows that
we really need a community-based solution.
Best wishes,
Arlo Griffiths
You could try this link perhaps:
Dear all,
I am looking for a digitally-searchable version of the Maitrī Upaniṣad, aka Maitrāyaṇīya, etc. Does anyone have any leads?
With thanks,
Cicely Bonnin
Cicely Bonnin BSc, BEd, MA(Adv)
Qld
Visiting Fellow, South Asia Studies, Harvard University (2023-25)
PhD candidate, Asian Studies, The University of Texas at Austin