In 1975, Pinochet offered to give Bolivia a small strip of land north of Arica in exchange for an equal amount of Bolivian land. However, the Treaty of Ancón forbids Chile to give formerly Peruvian land to other nations without permission from Peru and the dictator of Peru did not want to accept this transfer. The strip of land is pretty worthless and would require quite a bit of investment to build a suitable port and improve transportation to it.
Perhaps the Bolivian need for a seacoast could be argued more forcefully before international arbitration regarding the area in the pre-1929 period, and an alternate Treaty of Lima involving Bolivia as well is signed? The idea was suggested several times between the War of the Pacific and the 1929 treaty. Perhaps the final result would be Chile receiving the southern part of Arica Province (not including Arica itself), Bolivia receiving the northern part (including Arica itself), while Peru receives Tacna along with guaranteed access to the port of Arica. Bolivia pays Peru 6 million USD instead of Chile.
