I think they made this a sticky thread for moms with grains/SCOBY to share for easy finding. Then you can update and folks can see whats available...but hey, it's a good spot for some questions about specifics too I guess (I'm not the OP, so /shrug)....
But yes, to super charge your water kefir grains...give them some Rapadura/Succanant and or a shot of molasses in that water. Some fresh squeezed juice will also help. If the grains are even barely alive, it's like a vitamin booster shot and they will take off.
You can use this to 'super charge them' between your favorite sugar/fruit brews too...I swear, I have half a jar of grains now, and I'm going to have to put them on a sugar diet, as they are reproducing like bunnies!
And for the other question, yes, you can grow your own SCOBY from a good quality, unflavored or messed with, store bought Kombucha, if you are careful and give it time. There was a thread recently in NT about doing this....search on 'growing your own SCOBY' or something like that. You want to find a bottle that fairly fresh, and that hopefully has a bit of a 'SCOBY' looking chunk growing in it for best results!
Here is the link. I gave directions about half way down the first page: https://www.mothering.com/discussions...your+own+SCOBY