Hi Mike, I have been a V-Strom owner since 2004. Givi makes a great assortment of top cases as well as another company called Shad. Most are easily mounted to your rear rack so if you find a used one for another bike keep in mind they are easily installed. Top Boxes are great for touring and commuting but just remember to keep the weight down to a minimum especially if you are doing any off asphalt because the high weight can cause some stability issues for new riders. I had a Givi luggage on my 04 and had no issues. Take a look at the V-Strom site: http://www.stromtrooper.com/
The folks over there will tell you what you should do, what you need to do, how you should ride and of course give you at least 500 options as to what is available for your bike even if you did not ask. Also you will receive a lot of opinions of what the V-Strom can't do or should not be tried. Blah Blah Blah.
Check out the V-Strom Rally at Ironhorse lodge. http://www.stromtrooper.com/events/396298-2018-eastern-v-strom-rally-stecoah-nc-may-17-20-2018-a.html
My Givi Top Case, "empty" on the Dragon 2008