The sterling silver bracelet, which was sold at Sotheby's London, has 11 Harry Potter-themed charms and the charity's butterfly logo.
Lumos aims to end the institutionalisation of children, creating community-based services that provide access to health, education and social care.
A rarely-seen watercolour of novelist Jane Austen went under the hammer at the same auction for £164,500.
The James Andrews portrait is one of the most famous images of the writer and will appear on the new £10 note from 2017.
It was commissioned by Jane Austen's nephew the Rev James Edward Austen-Leigh in 1869 to accompany the Memoir Of Jane Austen, his influential first full-length biography of the novelist.
A spokeswoman for Sotheby's said it had been bought by an anonymous private collector.