Where can I purchase destrol it is a weed contract killer product for path and drives? ...

Furtilizer for Rasberry and Grapes vines?
Answers:    Here's a website that may get you started within the right directions:

http://www.spray-chem.com/destrol.html

good luck
What is an effectual channel to prevent moss...
No conception what destrol is, but you can use any total kill product and obtain same results.
Read instructions before you start