You can replace the bearing, I did mine not too long ago. But I wouldn't attempt it whilst still attrached! Remove the compressor from the vehicle first, which will mean de-gassing and regassing when done. Removing the compressor is surprisingly easy - just 4 bolts + the two for the pipes, one electrical connector and she comes out through the gap in the wheel arch. At least she did on mine, but then again I have a JDM one so a right hand drive - yours may not be so easy! I am also assuming that your compressor uses the same bearing as mine:

You need a 35BG05S16G2D - Air Con brearing, 35 x 55 x 20
It is £16.50 +vat and shipping. I got mine from Bearing Supplies Limited - 01603 891800 in the UK, but I'm sure you'll find one nearer.

Section 1A of the workshop manual available to download from here describes the process for replacing the bearing.

You can get a smaller belt to bypass the aircon whilst it is off or if the noise is unbearable.

I hope that helps and good luck.

Nick