All perfect praise be to Allah, The Lord of the Worlds. I testify that none is worthy of worship except Allah and that Muhammad, is His slave and messenger.
The practice of making pendants in the shape of the Prophet's sandals to be worn as charms or amulets around the neck is a religious innovation. It has been authentically narrated on the authority of ‘Aa’ishah that the Prophet said: “He who innovates something in this matter of ours (i.e. Islam) that does not originally belong to it, will have it rejected.” [Al-Bukhari and Muslim]
The Hadeeth in reference that was narrated by Ibn Mas‘ood is authentic and was cited in Saheeh Al-Bukhari. However, it has nothing to do with Tabarruk (seeking blessings from the Prophet and his traces). Rather, it is linked to Ibn Mas‘ood serving the Prophet by carrying his sandals for him. Therefore, it cannot be used as evidence in this regard.
Lastly, it should be noted that authentic reports have been narrated confirming that the Companions sought blessings from the actual traces of the Prophet like his hair and the remnant of his ablution water and the like. However, this does not apply to such items like the pendants in reference.
Allah knows best.