Making svg stay in place on window resize

regarding the following pen:
https://codepen.io/kravmaguy/pen/mogVJw

there is a red ellipse on top of the light bulb, I wish it to hold its position on top of the bulb and its size relative to the light bulb. Im going to make that ellipse svg into a little flourescent light so it has to stay on top of the light fixture on the cieling.
Its working on larger screen sizes but if you resize to smaller width you will see its not holding its position on top of the light fixture and its sliding off. How can I fix it?