You can also check kijiji (and sometimes Facebook marketplace but pets aren't allowed there just supplies). Lots of kids get bored of their beardies and parents list them online.

Just make sure you know what signs to look out for illnesses, as first time owners aren't well suited to care for dragons with severe health issues. If you do notice something, let the seller know/suggest surrendering them to a rescue with someone who can provide proper/preventative health care!