Amazon offers Prime members the Nathan SonicMount Universal Smartphone Armband
in Black/Sulfur Spring, model no. 4934NBE, for $22.33
with free shipping
. (Non-members can spend $35 or more to qualify for free shipping; otherwise, shipping costs $6.83.) That's the lowest total price we could find by $3, excluding the below mention. It fits most smartphones and cases via its center stretch elastomer and no-slip side grip.
A close price: REI has it for $16.93 plus $5.99 for shipping