I think it’s desirable that whichever stove you chose, it scales well with the rest of the project. A 111 is a great stove but is probable bigger than you want or need. I like the idea of an 8R, preferably an older model with the control knob instead of the key. You can probably find one of these for $100 or less. If it needs work, all of the parts for rebuild are still available. Then paint the case to match the Vespa and “Voila”! Or should I say “Bella”!