Replacement reflector for Hagen Glo ?

[magnosis]

Has anyone been successful in replacing a (dual-bulb) Hagen Glo reflector with a non-Hagen reflector ?

And if so, did you notice a big difference in light output ?  (I'm guessing if there's any difference, it would be about 2-4% at most, which is really negligible, but I might be wrong)
How do they compare in price ?