Using it like a Begged is the trick. For Klayim, the only Hetter is the fact that you aren’t viewing/using it as clothing. You are merely using your back as a convenient surface for showing your goods. I mentioned earlier the Beis Yosef that says explicitly that although we are only wearing it because of the Mitzva, it is a Begged.
Also mentioned there was that even on Shabbos you would be allowed to wear it at night, since the string are an adornment, which leaves up wondering, what did Avraham Avinu do on Shabbos to be Yotze doing a Melacha?