I cannot find another adapter that fits this specification. (Maybe I do not know the terms.)
It is a positive center, DC in: 12V 3A. The device itself is an Anker AH221. I tried to measure the head, and I think it is 1/10th an inch ~2.5mm.
The symbol is only a half circle--nearly everything on Amazon I find is 3/4th a circle, with https://www.amazon.com/12V-Power-Adapter-Supply-2-5mm/dp/B00447C4HM being an exception. However, it is only 1A, and the reviews claim that a 2.1mm ships instead.
The dot in the middle indicates the center conductor while the partial ring around the outside indicates the outer conductor, how much of the partial ring is drawn is just a style thing, it's not relevant.
Generic DC jacks like that come in 2.1mm and 2.5mm center pin. Unfortunately the 2.5mm size seems far less common nowadays than the 2.1mm, so if you do indeed have a 2.5mm center pin that limits your options.
Amazon is not a good place to buy this sort of thing, there are many third-party sellers on Amazon with dubious business practices, either selling substandard junk with non-existent or fraudulent safety certifications and/or selling items that do not match the listing. I would suggest buying power supplies from reputable electronics distributors.
A 2.5mm DC plug will fit a 2.1mm socket, but contact is likely to be poor, a 2.1mm plug will not fit a 2.5mm socket. Unfortunately it's quite hard to tell the difference visually.
I plugged the voltage, current and connector size requirements into the parametric on Newark and it found a single product that seems to fit the bill. https://www.newark.com/mcm/58-18265/12v-3a-inline-ac-power-supply/dp/33AC3039 , other electronics suppliers may also have suitable products.
