Have you checked out the Kichler website (www.kichler.com)? They have lots of different styles of attractive bathroom lighting. That is where we found sconces and mirrors to coordinate with our Moen (Eva) fixtures.

As s source of anything but decoration they are a big waste of gas unless you use a mantle. And then the flame is no longer visible.

Overstock has lots of fixtures in your price range. I like your idea of constructing something of translucent material to diffuse the light from the existing fixture but that sounds like a tricky project! Our main floor bath is smaller, maybe 5 x 8, but a two-light fixture provides plenty of light (including the tub/shower). Our fixture overhangs the mirror so the light seems to be amplified. I'd think that either 3 or 4 bulbs would provide the light you need. Maybe looking at photos of baths can help you decide what style you like. For example, do you prefer something linear or something with curves, as shown in this example? Here is a link that might be useful: Another Overstock option

A never nice fixture. The closest I have would be something like this: https://www.stridelighting.com/product-p/ch59065rb20-up5.htm