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The Rio Ucayali is a major tributary of the upper Amazon in Peru. There are dozens of apisto species known from the system, too many to list in a post. MacZ has given you one resourse. Another is the apisto species list on TomC's site: https://www.tomc.no/page.aspx?pageid=127.
I think for you a habitat type would be easier to manage than an exact location. Like an Igarapé, a Morichal or a pool in the Igapó around a certain lake or river.
I for example have done a small side tributary of the Rio Negro. And that kind of habitat can be any small blackwater creek along the main River. I chose one widespread species (Nannostomus eques) and one specific for the region (Dicrossus filamentosus) that is still common in that place.
I guess for a strict recreation of a locality you will have to go there in person or get someone to send you good and extensive footage and water analysises and maybe even send you the fish. That said: Availability of species should also be your concern.