mobiBlu-size headphones?

My new cube player thankfully came with a headphone, but I just realized its jack is a little smaller than regular ones.

Anyone who has one, or at least knows the mobiblu that well, as to what size jack it uses, and knows any site that sells quality headphones? Specifically, I'm looking for something like Sony's buds that lodge inside your ear.

Thanks.

how do i rammed headphone jack in?

C:) stick it in