Meritline offers this 3.5mm Male to 2.5mm Female Earphone Plug Adapter
for $1.79. Coupon code "MLCKX04HNL1" cuts it to 39 cents
. With free shipping
, that's tied with our September mention and the lowest total price we could find for such an adapter by $1. It allows you to plug a 2.5mm earphone cord into a 3.5mm jack.
Expect it to take two to three weeks to arrive.