The 5cm f2 Sonnar is a great lens, but as you saw in the first photo, needs a hood.
It uses 40.5mm filters, and the Russian push on hoods for the J-8 and J-3 work perfectly. I just gave my last one away. I use one from an old Nikkorex 35, which also uses 40.5mm filters.
Making one out of a plastic bottle is not hard, I've seen instructions on the Internet for doing this. I believe the person used a plastic milk jug for it. It's about the right taper for it.