Actually that's a R. Temporalis, not kersternii. The pygs are notoriously misidentified/mislabeled. Kersternii look a lot like brevs with the horizontal stripes but have longer tails and a lateral ridge of spines down the side. I've never seen anyone with them, which is what made me suspicious at first that babies were being sold. Now it is possible that this could be kersternii, not saying that's not an option, but it looks like a brev and the pic you posted as reference is a usambara pitted pyg (temporalis). I have a great text at home with better pics of the species correctly identified so when I get home I can post some scanned pics for reference from that book.
These are excerpts from Petr Necas and Wolfgang Schmidt's "Stump-Tailed Chameleons; Miniature Dragons of the Rainforest", Chimaira publishing 2004. I have no affiliation with the authors or the text (aside from loving it) and in no way take credit for the images. Posted to enable the OP to identify her adorable new addition correctly.
R. Temporalis
Their defining characteristics are their pointy mouths and the diagonal stripe with dots. They have longer tails than adult brevs.
R. kerstenii
Their defining characteristics are their very distinct narrow stripes, a lateral ridge of protuberances and much longer tails than brevs. The stripes cause confusion with the brevs when they are showing a very striped pattern for some people.
The next images are mine, were taken by me and I claim all credit for them!
Defining characteristics of R. brevicaudatus are the small beard under the chin, lateral broad stripes, and relatively short tails (especially females).
Male R. bevicaudatus
Female R. brevicaudatus
Neonate male R. brevicaudatus
I hope this helps!!
OP: I'd put down money that you have a baby female R. brevicaudatus.
As a former breeder of pygmies, that picture you have is definetly a Brev. Sorry to burst your bubble. Not to say that a Brev is bad. It's just less rare. I love Brev's. Those were my main species of breeders. The beard is a solo spike made from large scales that sits right under the lower jaw. Its pretty unmistakeable. Hope this helps.