Now if you are from the USA you probably know what an egg crate lighting grid is but I'm from the UK and didn't have the foggiest idea! So more trawling and googling later I found an alternative grid in the UK it's a pond filter grid and can be found on eBay for about £7.50 including delivery. I also found a 9L really use box box that would hold all my promarkers with spare slots to accommodate future purchases.
I then used tie wraps to secure the top grid in place through the holes I'd made using my versa-tip tool.
I spent a peaceful afternoon in the sun colouring mini sticky dots and sticking them to the relevant promarker pen.
links to some of the products I used...