Navigate the throng.
Castelli makes several large capacity kit and travel bags, but when you're also pushing a bike, then the rolling suitcase-style option is simply untenable. The Gear Duffel Bag is a different story. It's got a shoulder strap and carry handles, so you can hoist it by hand while wearing a wheel bag on your back or throw it over a shoulder while piloting your bike through the registration table throng.
It's also water and stain resistant and features internal organization pockets and reinforcement along the bottom to keep your kit organized, dry, and damage-free until your event. Afterward, a vented external pocket gives you a spot for your bibs and socks to maintain a separation from your bottles, helmet, and other items you'd rather not have mixing with a post-race chamois.