I have been shopping for a tail bag for the VF500, haven't seen much that I like (read prices). I was browsing at Wally World today and spotted this toiletry bag for $10. It holds quite a bit of stuff, isn't too obtrusive. I bought a cargo strap with a Fastex buckle (also at WW), I'm going to have the wife sew it to the bag and loop it under the seat as shown in the pic. It is not waterproof, but wife is going to make a rain cover for it.
Nice work. I've strapped a small duffel to the back with bungee cords before. For small stuff I use my magnetic tank bag I got from motorcycle superstore. Its a fieldsheer, and i think it cost about 50 or 60 bucks.