Why do you want a replacement?, it doesn't look broken - and ceramic filters don't normally go faulty (unless you physically break them).
Looking at the service manual, it appears to be a low-pass filter (LPF11830KH) - so presumably a 118.3MHz low-pass filter? - it feeds the aerial connection to the FM tuner input.
I would imagine a replacement would need to be sourced from Alpine?.
But again, are you sure it's faulty?, and why?.