where can I go to shop for yoyo string or even just get a different kind of yoyo string than on YYE. :-\
There are other yo-yo stores that sell string but it would be disrespectful to YYE to mention those here. One favorite among players is GString.
You can make your own, or you can buy some homemade strings on the B/S/T.
Such as…
Whip yoyo string:http://yoyoexpert.com/forums/index.php/topic,14792.0.html
Sick String:http://yoyoexpert.com/forums/index.php/topic,10657.0.html
Mirage String:http://yoyoexpert.com/forums/index.php/topic,13943.0.html
Those are good ones, but there are many more on YYE forums.