I think I might have a solution. Its not as nice as the true bloom effect, but I think it will work.
I create a box with the base material I created.
Then, I put a white box at the mid-line which slightly protrudes outside of it.
Next, I put instances of BP_DoomGlow on the sides of the white box and made one tinted blue and the other tinted red.
Here is the result:
I am going to have to tweak it.
For the sphere, I am going to have to create a bunch of small flat panels all the way around the circumference since the glowing bit will actually be a flat surface.