I found only 6" on Amazon :).

https://www.amazon.com/KITOSUN-Multicolors-Celebrations-Centerpiece-6inchX1-4inch/dp/B071998G5C/ref=sr_1_fkmr1_4?ie=UTF8&qid=1541690496&sr=8-4-fkmr1&keywords=led+light+7%22+hookah+holder

But you can try to search the eBay, I think too ^^.

Or do it yourself at home. Buy rubber self-adhesive pads with a height of about 5mm and stick them on a glass vase. Then you can put under your vase whatever you produce yourself - for example on the mentioned unused DVD media, the RGB LED strips will be stuck and cut, for 12V power. Of course you also need an adapter 230V > 12V.

​