It's a standard slimline bay. Any slimline blu ray, dvd, cd etc drive will fit the bay. You will have to CAREFULLY remove the face plate from your current drive to put on your new drive so it will fit the contour of the G73JH notebook correctly, and of course it won't say blu ray since the plate will be from your DVD combo, but you will know it's there.
Finding them at the moment has been a little tough. Newegg had the sony's for a while that would work, but they don't show up on a search right now. I prefer pioneer and teac over sony, but have not yet seen any in stock.
From what I understand on the blu rays, they have been having issues with the drives in the slimline form factor. That's why the A1's haven't been available.... drive issues with the blu ray drives.
Honestly, unless you need the playback for blu ray on the go, get a USB 2.0 blu ray burner. Cheaper than the slimline will be and just as effective for burning and playback. Just not built into the machine....