As far as I know, most of the self-suspension devices (like the CB3000, CB6000, and the curve) are all relatively comfortable for frequent movements. If you're looking for metal belts, you should consider the thong/sport/cable styles from various manufactureres (e.g., neosteel, lockedinsteeel, tollyboy, wj), as I hear they tend to be the most comfortable rear styles for regular and repetitive movements.