Glass is a bad idea IMO & IME -- reduces light and oxygen, neither of which is good for a reef.
I have some new fish that are VERY special to me, and I'd be heartbroken if they went surfing, so I decided to replace my eggcrate - it's great for larger fish, but small wrasses can easily jump through it (this is how I lost my Lubbock's).
I ran a search on tops earlier this week and found lots of threads referring to the above type of setup using garden netting and window screen frame. Went to a home improvement center and bought netting (in the garden center, the stuff that's used to keep birds away from cherry trees), window screen frame, corners, spline and a spline tool. It all cost about $30 in total, and turned out great. I tripled the screen, with one layer straight, and the other two at opposite angles. The holes are much smaller than the eggcrate, and the frames are very sturdy. I really like this alternative, and highly recommend it.