KSH password generator

how to make sure the generated passwords contains all these special characters (?!/=) ?

Currently I'm using:

pwd_usr["$i"]=`cat /dev/urandom|tr -dc "a-zA-Z0-9-_\?\!\=\/\"|fold -w 15|head -n 1`

But some of the generated passwords might not contains the special characters I want. Please help. Thanks.