I don't have any experience with Mogami 2803 but have made several pair of interconnects with Mogami 2534 Neglex Quad microphone cable. It's very easy to work with, thin, flexible and copper shielded. It's got four 24 gauge conductors so doubling them up gives you the equivalent of 21 gauge.
It's available from takefiveaudio.com for about $1.15 a foot or markertek.com for about $.80 a foot.
It's available from takefiveaudio.com for about $1.15 a foot or markertek.com for about $.80 a foot.