There's this.
You can't run it at the same time as Endless Pixiv Pages but it's still pretty useful.
Posted under General
Yeah, I'm using it, but there are only 1000 pages you can look through on a certain tag so I miss a lot of high ranking pictures. 1000users tag helps a little but most pictures with 100-999 favorites are being left out.
Well, one way or another I hope sorting by score would become possible on Pixiv in some near future.
If you're using the 1000 users tag, there are also tags for 100 and 500 user tags. Since there's no standard on pixic, not everything is usually tagged as such though. You can try slapping on 100 on the end of tags or their common abbreviations to get both 100 and 1000, like for とある100.