Yes, there are actually two ways to do this.
First, you can set the character that you want into a variable and then use that variable in the $pos:
var %x = (
echo -a $pos(stringhere,%x,1)
You can also use the $asc value of the character:
echo -a $pos(stringhere,$asc(40),1)
The values for the characters you asked for:
( - $asc(40)
) - $asc(41)
" - $asc(34)