Can I offer some suggestions about searching for parts?
A huge advantage is gained if you know exactly what you are looking for, so the first step is to find illustrations or photos of the missing bits. Parts lists, brochures, magazines etc can be useful, otherwise photos from a good (original) surviving bike.
Doubly useful are some measurements, or a brand name for an accessory like a headlight.
Remember, no-one other than you is restoring an XO Triumph right now; most people wouldn't know an XO Triumph if they saw one, and certainly no-one knows what the gear change lever looks like! But that doesn't mean they don't have one hanging on the shed wall, without knowing what it came from.
Perhaps you could post a photo if you have one. If not, perhaps you should be asking what a Model XO gear change lever looks like!
Cheers
Leon