Sorry for the late answer, just found the question today:
I can recommend Reconnaissance. It's easy to use and also has a neatly arranged hex and ascii view. It is also what I used back in the days.
^ Only very few sector editors offer such wide petscii lines. This increases readability - each directory entry equals one line. The program "sector ed." starts at track $13, sector $00. The filetype is standard prg as defined with the $82 left of it.
Just like you, I need a sector editor (my nordic power cartridge sometimes saves files with a wrong load-adress to disk).
So I tested literally a dozen other sector editors today. In Vice and/or on my physical machine - just to have a look. (It took quite a while ;) One of the best was "Satans Seed" aka "Satans Cracker" by "the deacon". Don't look at me, I didn't label it that way ;)
If you want small size the winner in my opinion is disc-doctor-V3 by kevin pickell using only 15 blocks.
You maybe can find these programs if you g**gle for "commodore.software" and "disk editors", but I'm sure searching the internet for the program names will work, too.