that aint speaker cables. and you cant drive speakers directly from a sound card, you need to connect it to a speaker amp first. unelss ofcourse oyu mean to connect your pc speakers, then yes, althought the pc speakers have its own internal amp.
as for that exact cable. its a two 2 x mono 1/4th to1/8 input. that one is for the emu0404 since its unbalanced (one channel for the 1/4th connector/mono, instead of stereo), although it could work with emu1212m.
as for where to get it, beats me. i think you can find one at places that sell cables (lol), but i dont know if you can find any very high quality mass produced one. someone else should know. but for expensive you can ask headphile or fid audio to build you one, they make cables for this sound card.