Glad you asked, said the guy with the Hume avatar. Hume seems to have written something quite close to not-self independently of Buddhism. To quote Hume:
I may venture to affirm of the rest of mankind, that they are nothing but a bundle or collection of different perceptions, which succeed each other with an inconceivable rapidity, and are in a perpetual flux and movement.
Interestingly, Giles mentions Parfit in footnote 11:
Parfit is one of those who fail to distinguish between the eliminative no-self theory and reductionism. Consequently, he mistakenly thinks that the Buddhist position supports his reductionism.
One thing that is interesting about Hume is that, despite having a theory of mind that is in many ways similar to the Buddha’s, he had a general moral outlook on life that was radically different. Hume was a worldly philosopher with a generally very positive outlook on commercial society and what the Buddha denigrated as the dusty household life. The Buddha was an ascetic world-renouncer, but Hume was a politically engaged bon vivant, who was contemptuous and dismissive of asceticism and mocked what he called the “monkish virtues”.