What can I use to make the cloth of a tee pee?

I think that is one word, teepee. Otherwise it looks like you're asking about some sort of outhouse.

Since canvas is recommended, I'd use canvas. You can get this at fabric stores or drop cloths from a home improvement store. Traditionally buffalo hides would be correct. Depending on your use for this structure I would think that any large piece of cloth like sheets, blankets, or furniture throws might suffice.

https://www.wikihow.com/Make-a-Teepee

A painter's drop cloth would probably work or a sheet. both are good sources for large pieces of fabric!

Use a canvas painters drop cloth. If it is going to be used outside, paint it with several coats of exterior semi-gloss paint to make it water proof. If to be used inside in a playroom,you can use acrylic paint to decorate.

Duck cloth

any durable cloth will do

Dependping on how you plan on using the tee pee, you will need different materials. For a child's play tee pee, just use a fun print that suits their interest. Lining it will make it more sturdy. For one that is going to be outside, you need a thick fabric like canvas. Some people even paint the fabric to make it more water repellent.