Have Scoby with no starter brew... help!

I acquired a scoby and some starter brew. I let it go for far too long and it is quite vinegary. I want to start a new batch. Can I use the Scoby and add a bottle of GTs? Can I still use the vinegary batch I made and just use a little as the starter brew?

Help!

Also, I haven't been able to find any unflavored kombucha anywhere. Could I use a raw, flavored GT?

You could use the SCOBY and raw kombucha tea. High Country would be a better choice, but GT should work--although I would try to not use flavored if you have a choice. The flavoring itself shouldn't harm the culture, but the sugars will throw off your recipe.

You can also use your SCOBY and a tiny bit of the starter or cider vinegar and simply build up your brew again by starting small and then adding more sweet tea once that has reached the right PH.

I also have a giant SCOBY I let go too long. I used a little of the culture and some of the starter and added to a new batch. Once that produced KT I added more sweet tea and the giant SCOBY and got things back on track.

Good luck.

Use what you have.
Your batch may be a little strong this next round but successive batches should be alright.
The whole purpose of the starter tea is to acidify your brew, what better than some really acidy vinegary tea?