Pet ownership creates profound human-animal bonds, making pet loss significant. However, compared to human loss, Human-Computer Interaction (HCI) has given pet loss less attention. Addressing this, we conducted an exploratory mixed-methods study. The study began with a large-scale survey (N=611) revealing critical challenges: a strong desire to preserve memories but limited support for continuing bonds. Built upon these findings, our participatory design sessions(N=10) co-designed Bondi, a tangible prototype supporting continuing bonds through multimodal and customizable interactions (e.g. touch, sound, and light), evoking pets’ unique sounds, tail movements, and lighting effects. We then conducted a three-week field-deployment study with four participants to evaluate how Bondi facilitated the maintenance of bonds with their deceased pets. Results showed that the customization and multimodality evoked vivid recollections, lowering the social barrier for grief sharing. Bondi fostered comforting and non-intrusive connections with pet memories. Furthermore, the study distilled design considerations for future pet bereavement support.