Great review of these fantastic pencils and great sketches indeed.
Me also I was taken ercently by these colors finding a replacement from Prismacolors.
I spotted to great alternatives, I don't know if you know them.
Koh-I-Noor PolyColor, very similar to Prismacolors and these Derwent ColorSoft.
Needless to say that I don't miss Prismacolors.

For even more carefree sketching jsut try some of the faber-Castell pencils. High in hardness but affordable and washable.

Cheers!