story identification - YA Series about a boy who gets a Aztec (?) armband, gains powers when tokens placed in it
I remember a book in this series around 7 or 8 years ago. I think it was newly published at that point, but am not certain. It was aimed at young adults, and I think the cover had a red border with artwork from the story.
The main protagonist is a middle school aged boy. I didn't read the first book, so I'm not entirely sure of how he got it, but at some point he obtains an Aztec armband with a circular indentation on it. When he places certain tokens or coins in that slot, he gains powers, related to whatever was on the token. These include invisibility, super strength, flight, and climbing on walls. In the book I read, I remember him crawling on walls in a sewer under the city. The armband was designed as a bracelet for a full grown warrior, but because the protagonist is a scrawny middle schooler he's able to wear it all the way up his arm and under his sleeve, so he can wear it all the time without it being seen.
The protagonist also has a pet lizard, and somehow is able to communicate with it. I don't remember if this is because of the armband, or for something else.
The antagonist also has a magical armband, but I don't remember what his main plot was. In the book I read, he steals some of the protagonists more powerful tokens, leaving him with just the wall crawling. He complains, but his lizard companion doesn't see why he dislikes the wall crawling.