Benson and Wells differ in their translation of ‘Panama’ into Esperanto, but Vikipedio, PIV, and ReVo agree with Wells. However, Vikivortaro agrees with Benson. Is Vikivortaro’s agreement with the idiosyncratic Benson merely a typo? – or is there some method to the madness?
None of these dictionaries is normative. There is, however, an official decision by the Akademio de Esperanto from 2009 (Listo de rekomendataj landnomoj), which has for the country:
Panamo [8a Oficiala Aldono, so this is the only correct form]
The city hence has to be Panamurbo (PIV gives the impression that the name of the city was officialised as Panamo, too, but 8OA explicitly speaks of the country).