i've been using that one for years and it worked fine for me

if you don't want to input the account #, they also have an option to buy vouchers you can input to top up your mullvad account yourself 

 Where are the vouchers? I don’t see it. Proxy one had that but no lightning option 

 the button after "Want to purchase a voucher without logging in?" 

 lol WTF, didn’t even see that. Should rename to buy vouchers :/ 

 Cool, it works!! Ty