Meritline offers this 3.5mm Male to 2.5mm Female Earphone Plug Adapter
for $1.79. Coupon code "MLCKY05QNL1" cuts it to 39 cents
. With free shipping
, that's tied with last month's mention and the lowest total price we could find for such an adapter by a buck. It allows you to plug a 2.5mm earphone cord into a 3.5mm jack. Coupon expires after 400 uses.
Expect it to take two to three weeks to arrive.