It ain’t picky about the voltage but the polarity probably has to be center-negative.
The JPN/PCE spec of 9v jumped to “10.5v” in the USA/TG16 spec, almost as if they just took an adapter intended for 100v and threw it into US 110-120v outlets, which scales the output proportionally with that type. The 10% to 20% input voltage increase results in 10% to 20% increase in output voltage. 9v becomes ~9.9v to 10.8v, which is roughly ”10.5v”).
It’s the most common size too: 5.5x2.1mm. Center negative is only common here in old Japanese game stuff or even older battery + DC jack portable devices (transitioned in the ‘70s).
Some Neogeo AES plugs will work (not the 5v ones), SEGA Genesis Model 1 (and Master System?), aftermarket NES (not the original that outputs AC), etc will work.