I need some help with getting more light in the cage.
I made my Gouldians a cage from an old armoire that I'm very happy with, and they seem to be too.

When I put it up on the bottom stand with the drawer, the cage elevated to the height of the window, and it's way too dark in there because light isn't going in near the top, where the finches like to hang out.
The sides are solid, the top is clear acrylic and the front and back are fencing/chicken wire.
Moving it or angling it is not an option.
Any sugestions on how I can get light in?
I was thinking of buying a small desk lamp and securing it to the top of the cage shining in, but I realized I'm not sure what wattage to use, or if that's even healthy for them to have a light beaming down on them...? I'm worried if it's an open bulb type, it might blind them when they look up?
I'm also fuzzy on what "full-spectrum" lighting is.
Any suggestions are welcome!
Ps I'm looking for very cost-effective ideas

Thanks in advance!