Hi Des, welcome to IIS
You'd have been better off getting an "el cheapo" Celestron from a camera shop than buying this scope. You're probably going to have to knock up your own counterweight for it as I don't think you can get another specifically for the scope. Any viewfinder from a dedicated telescope seller would be infinitely better than the cheap plastic crud on the scope you bought. Try
Bintel. Actually, what you should do is save up for awhile and get yourself a proper telescope. The cheap toy you bought second hand will only be a source of frustration and disappointment for you and you'll most likely trash it at some stage, anyway. A Skywatcher 6" dob (alt-az reflector) from the guys I mentioned would be infinitely better and more usable than the dse scope.