Purity: Procuring Materials for Tayammum

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 679:

If a person does not have anything with which to perform tayammum, in the event that it is possible, he must procure it by purchasing it and suchlike.

-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)