There's a lot to say about the usage I guess, but to make a long story short:
Me is a so-called objective pronoun, opposed to subjective pronouns (I, you, she, he). It's called like this because it's placed in the object field after verbs or prepositions:
Wait for me!
She likes me.
Myself instead, is used with reflexive verbs, meaning those verbs that indicate an action that "falls" on the subject:
I wash myself.
I told myself it couldn't be true.
There are exceptions, you can find them here, but I'll paste the interesting part:
Usage note: There is no disagreement over the use of myself and other -self forms when they are used intensively "I myself cannot agree" or reflexively "He introduced himself proudly". Questions are raised, however, when the -self forms are used instead of the personal pronouns ( I, me, etc.) as subjects, objects, or complements.
Myself occurs only rarely as a single subject in place of I: Myself was the one who called. The recorded instances of such use are mainly poetic or literary. It is also uncommon as a simple object in place of me: Since the letter was addressed to myself, I opened it. As part of a compound subject, object, or complement, myself and to a lesser extent the other -self forms are common in informal speech and personal writing, somewhat less common in more formal speech and writing: The manager and myself completed the arrangements.
There is ample precedent, going as far back as Chaucer and running through the whole range of British and American literature and other serious formal writing, for all these uses. Many usage guides, however, state that to use myself in any construction in which I or me could be used instead (as My daughter and myself play the fluteinstead ofMy daughter and I) is characteristic only of informal speech and that such use ought not to occur in writing.
This usage is justified by the usage notes in Merriam-Webster Dictionary of English Usage and the Merriam-Webster Collegiate Dictionary. See my answer to You and Yourself, Me and Myself for a discussion of the grammaticality of myself in non-reflexive constructions.
This usage probably comes from discomfort people have with selecting pronoun case in coordinates. There is a rule in informal English that you always use accusative case in coordinations of pronouns regardless of syntactic position (“My brother and me are hardly on speaking terms these days.”—you can find many examples like this in the Corpus of Contemporary American English), but there is also a rule in standard formal English that those kinds of coordinations are ungrammatical and you must use the nominative case. As a result, people are uncomfortable using either me or I because their intuition leads them to say me but the formal grammar they learned in school draws them towards I, so they “split the difference”, as it were, and use myself.
Edit: Shinto Sherlock correctly points out that the second example usage in the question is in fact a perfectly normal use of reflexive myself. I’m not sure either why it would be a surprising usage.
Myself is a reflexive pronoun. It’s called that because one of its uses is to reflect the action of a verb back onto the subject, as in ‘I’ve hurt myself’. Yourselves is used in the same way in the sentence you quote from ‘Harry Potter’.
Reflexive pronouns are also used for emphasis, and that is how myself is being used in ‘I myself don't like this idea’ (although that would probably occur as ‘I don't like this idea myself’). That is also how it is being used in the second part of the ‘Harry Potter’ quotation.
Best Answer
"Someone like me" is the correct one.
There's a lot to say about the usage I guess, but to make a long story short:
Me is a so-called objective pronoun, opposed to subjective pronouns (I, you, she, he). It's called like this because it's placed in the object field after verbs or prepositions:
Myself instead, is used with reflexive verbs, meaning those verbs that indicate an action that "falls" on the subject:
There are exceptions, you can find them here, but I'll paste the interesting part: