Plextor PX-W1210 Optical Pickup Unit replacement

My Plextor PX-W1210 reads CDs, writes CD-R but has trouble writing CD-RW. I am thinking of replacing the Optical Pickup Unit. I think the drive is based on a Sanyo chipset. But what make and model is the Optical Pickup Unit in this drive (12x10x32 CD, not DVD)

To help identify the optical pickup unit inside my PX-W1210, here is a photo. The sticker on it has code ‘wx3484f4h’. Thanks.