I get it. You're trying to make face masks and all of a sudden elastic is nowhere to be found. Don't panic. The absolute easiest substitute for elastic is using a knit fabric to make ties. Knit is the dream fabric in this scenario because it won't fray or break down during laundering, so you can easily just cut strips of knit (you can even cut up an old t-shirt) and now additional sewing is necessary to make a wonderful elastic substitute. What's more is that the knit will not break down like elastic will under heavy duty sanitation processes (like they use in the hospitals) AND I think it's way more comfy. You can also use bias tape or binding tape to make straps. This is not my favorite way because it takes a lot more time to sew and ties with no stretch don't seem to be as comfortable or as well-fitting as stretchy straps. Just use the knit!! Both my filter pocket tutorial and my 5-minute serger mask will show you how to use knit straps in lieu of elastic.