I do approximately 20 quizzes a month, not all are of the calibre or style of Rainbow - some are what I call coffee break type though others need lots of research.
As I've been doing them for years many are repeats from setters but I also source mine from the 'Monthly Quiz Round up' on...
http://www.theanswerbank.co.uk/Quizzes-and-Puzzles/Question1494724.html- you need to register to ask and answer but not to browse.
and
Fundraisinfquizzes.net - you may need to register to access the quiz list.
I try to give details when quizzes are asked here too if I can to help other quizzers boost the coffers of the charities.
Note to admin - if my post is deemed as advertising another site feel free to remove it.