Is there a way to find the next/previous (in document order) element with tabindex="0"?

The closest I’ve gotten is:

                case 'Tab':
                    let item = node.closest('.listbox').nextElementSibling
                    do {
                        const focusable = item.querySelector('[tabindex="0"]')
                        if (focusable) {
                            focusable.focus()
                            break;
                        }
                        item = item.nextElementSibling
                        if (item == null) break;
                    } while (!item.querySelector('[tabindex="0"]'))
                    break;

but this stops at the parent level.