Hi Sam.w
I would like to recommend you to read this thread, it is a bit old (note to oneself update it,
I accept volunteers to help 
) but it will give you a very great feeling of what differentiates diabolos
http://diabolo.ca/forum/index.php?topic=3166.msg38358#msg38358and read a bit around here, it is normal to feel confused at the beginning do not worry
http://diabolo.ca/forum/index.php?topic=3.msg3#msg3Once done that I would suggest to read about the following diabolos (use the search feature of the forum, up and right corner of the website, and read some titles of the Gear board): Taibolos v2, Sundia EVO and previous, Epic diabolos, Circus, and Finesse. Any of these is very good, although some are better.
About the weight of the diabolos this is something that can be found in maximum 3 minutes using google. But let me help you this time:
http://lmgtfy.com/?q=sundia+EVOLUTION+weightAbout the selling websites, we usually do not list them in the forum. You can PM somebody if you want advice, but it should be easy to go to google, check the price of the diabolo, check the shipping cost, take a calculator and choose the cheapest for a given diabolo. We can also discuss whether we want to list hem or not. Maybe it is a good idea.
If after this you have questions that are not related to Sundia EVOs better create a new thread, or look for an existing one that contains the info you are looking for.
Welcome, good luck, and have fun