The true measure of your success is what you are seeing in the fit of your clothes, you are changing your shape and getting fitter. Congratulations on that!
That being said I weigh in every day, it's how I start my day on or off program, when I stop weighing in I have in the past started falling off my program, so it's kind of a security blanket for me, I really need to wean off of it. I wish I could do what you're doing.
For years I had a conair weight watchers scale, it worked great, I think you can get one for maybe $20 or maybe even less, the trick with the scale is not getting hung up on daily fluctuations, that can drive you crazy, only compare week to week, or beginning and end of month.
I just upgraded to a WW scale that gives body fat measurements as well, I got it at bed bath and beyond with a 20% off coupon you can get if you sign up for email offers. The first one didn't work after a couple days, they (bb&b) took it back, no questions and gave me another one that has worked like a champ for a couple of months now.
Best of luck and again congrats on your success so far!