We generally avoid adding models not sold in North America to our lists, to keep them from getting too long, but that doesn't mean you can't search for them. You can type any model name into the Model field, and AutoTempest will search for it.  So in this case, I'd recommend choosing Aston Martin as the make, and then typing Cygnet into the model field.  You can also set other filters if you wish.  (Though they're going to be relatively rare, so it might not be worth filtering further.)