This study explains the constructs of a purchasing portfolio model (PPM) that defence authorities can use in practice in defence procurement and designs a segmentation model. We identify open PPM design and application questions in the literature and conduct a Delphi study with twenty experts from Swedish defence authorities to design a segmentation model that is fit-for-purpose. The paper addresses the open design and application questions discussed in the literature and satisfies the operational requirements of the Swedish Armed Forces (SwAF). The proposed segmentation model builds on three dimensions: the operational requirements of the SwAF, the market's ability to deliver supplies on time, and limitations in the SwAF operational capability if the market does not deliver supplies on time. To reduce complexity, we propose a two-stage model in which we use one dimension as a precursor to a two-dimensional model. In the latter, we merge sixteen elements into one square along with three other segments which users should treat differently. The paper contributes to extant academic knowledge on PPMs by eliciting practitioners' views on open design and application questions. We develop the proposed segmentation model in cooperation with practitioners and believe that it will be of value in defence procurement practice.