Welp, I found a fairly low-cost alternative to "real" marquee brackets.
I was at Rona, which is a Canadian chain exactly like Home Depot, and in the "do it yourself screen window" aisle, there were these long plastic (or vinyl?) strips that are shaped like this:

*Note: The green lines I drew in cuz the flash washed out the detail. The green lines show the shape of this part.
The long part is about an inch wide. Then there's a channel just perfectly sized for a marquee's thickness, and then there's a short "front". On the very back , you can see a little "lip". This lip will be nailed to the wood panels with very small nails, or a staple gun.
These are not as solid as steel brackets, but the beauty here is they are flexible, so
if your top panels on your cabinet are a little angled like mine, then the marquee will still sit straight since it flexes a bit.
The plastic is light enough to cut to size very easily, and you can buy this spray paint that adheres to plastic to color this as you need.
And here is the best part: $2.39cdn for 8 feet of this! That's about $1.79 us!
~Ray B.