Eureka's US E0106 page identifies a pre-motor filter for NEU100. The code is attached to both the replacement part and an exact upright model, which is more useful than a generic 'Eureka filter' search.
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How to avoid a wrong part
Locate the model label and the pre-motor filter compartment according to the NEU100 manual. Other Eureka filtration pieces may sit elsewhere in the airflow path; the E0106 relationship does not cover them or another PowerSpeed model.