On Clips4Sale, lol. Unless someone bought those clips and decided to generously share them out on the internet - there's no way to get them, other than buying yourself, obviously. I don't know if those clips have been leaked out in full size yet. It seems like not. So you'll just have to wait until it happens (if ever).
For all the old Klixen clips - yes, WMV is the source from Clips4Sale. The mp4 files of those are reformats and dumps from over the internet. And usually they all have a bit worse quality than original files. Though it varies. There are some very good looking mp4 files, almost identical to original, but it's usually achieved by some buff of bitrate, which results in bigger file size. If you want, you can go to the file properties and look at the bitrates yourself.
there's a decent collection in the thread I linked below.
Maybe those people and you should read attentively and see that I'm specifically talking about the old clips with Klixen herself, and that I'm answering someone's question about the original source format of those clips, which is wmv.