my parents arent too keen on me having another herp either!
i know that the only way to get them to let me have another is if i adopt one from the rescue which i volunteer at, because im giving it a second chance!
have a look for rescue centers, go to your local rspca and see what you can do!
or find someone who has snakes and take your dad to handle them (thats what i did)
do LOOAAAADS of research buy some books and show your dad that your'e swatting up on herps, and show that your'e truly interested!
btw: there are some shows coming up, eg: the IHS one....