Bunnings have a big solar light around 30cm which would be easily made into a pixel. They are our version of the really big light that the US people can get.
Similar to these but only $15.
I have never had any real luck using a sponge. Swapped over to using one of these instead. They are available from Jaycar.
That is a good looking star, is the main frame box or flat bar? I was thinking I need to change the one I made last year from steel to alloy.
Here is a 1300mm tall Bethlehem star, from memory I think it has 180 INK1003 pixels on each side. Still waiting to get a tree to put that on top of....
Welcome to ACL Shimmer, it's great to see that you have dove in deep & getting stuck right into making a display. If you keep going at this pace you will be blowing the big guns out of the water straight up.