I just received my HS12YHA 120 GB drive and installed it in my iPod. I got mine from abestelectronics2011 on eBay and there are still
9 remaining for US $34.40. It came packed really well, in pristine external physical condition with SMART data showing it's new and good. Others are also selling these cheaply.
This drive is thin like MK3008GAL, so it can be installed into a 30GB iPod with the original case back. It has 4K sectors, so both the bootloader and Rockbox must be recompiled with MAX_PHYS_SECTOR_SIZE changed to 4096. That #define is found in the config header for the device you're using, in firmware/export/config. It's also a good idea to align partitions. I did that manually in fdisk. The OF and iPodLinux work fine without modification.
The drives don't come with iPod foam and bumpers attached, but those aren't hard to remove from the old drive. The foam was held on with strips of double-sided tape which may be hard to remove from the old drive. I used some new removable double sided tape to attach to the new drive.
Yeah, I know solid state upgrades are possible now, but having a spinning disc is not a problem for me.