Respiratory masks are not available for purchase in most areas of the us. are there any alternatives a person use as a temporary substitute - towels, handkerchief, cut up sports bra or clothing, etc?

Likely unnecessary..: Most of the visuals we see of this disease come from countries where it is a social taboo to be in public with a runny nose & not have a face mask. The mask need is oversold while simple methods like frequent hand washing & social distancing are more helpful. That said if you want a mask go to a tool/store like Harbor Freight/Home Depot/Loews, etc where they sell simple masks to exclude dust.