I understand your issue, very much a perfectionist.
Its never perfect, there is always a give-and-take in these situations.
Question: How important is the lamp to you, and how important is it to the player 
Most players would just run by and not think about it at all.
There is somewhat of a medium solution here, have a one sided circle plate in the top facing the light with a semi-transparant surface that you tweak until it’s to your satisfaction.
But that can be very costly for just a lamp. especially if you place allot of these throughout your scene. At some point you will have to compromise on something, games are allot of smoke and mirrors. 