The Oxford Dictionary of Phrasal Verbs classes this usage of the transitive multi word verb get back (= 'recover [something] [one previously possessed]') as optionally separable, meaning that the orders
[simplex verb] [transitivising particle] [noun phrase] and
[simplex verb] [noun phrase] [transitivising particle]
will both be met with.
However, ODPV stresses in the preface that with such multi word verbs, it is far more idiomatic to postpose the particle with short NPs (indeed, it is ungrammatical not to do so with prepositions):
- If you lend him your gloves, you'll never get them back. [not get back them]
- Did you get your car back from the garage? [get back your car rather unusual]
And the reverse is true with weighty NPs:
- Did you get back that marvellous tool for extracting tacks and nails that you lent to Alice?
The NP 'a part of my money' falls in the middle lengthwise; you can confidently separate the MWV get back, or choose not to. Claims that only one variant is acceptable / normal are overprescriptive.