Harold,
Your local auto body supply store will carry all the 3M "Fine Line" plastic tapes they use in the industry.
I use much of the .25" green tape for straight lines and some corners. I use the blue tape for corners. I use the .125" in the blue. Makes a tight corner. Not easy to mask the .125" tape but if careful it can be done and done well.
I have a paint Build on the 007 Flite Streak over at CFC Graphics, pictures and all using both tapes.
I wouldn't recommend anything I don't use myself.
I'm guessing you can Google for these products and find them on line.
Here's the proof of the pudding, my Skyfall 007 Flite Streak. Both those tapes were used and, as you can see, they leave a great edge!
Plastic tape is all I use except if I cut a mask. Masking material leaves the same kind of edge. Perfect.
Good luck.
Charles