nuisance: have you got a photo of your cover? Sounds like a great idea!
Here's a pic of what I just did. I made an 18" x 24" cover for the cooktop from a piece of 1/2" cabinet grade plywood, glued a piece of laminate to it and trimmed it off with maple edging all around. I made a support at the front and at the rear, I traced an outline of the cooktop on cardboard and transferred it to a piece of maple. The new top locks in place between the wall and cooktop and won't move around. It sure adds a lot of useable counter space and you can prep stuff on it. We'll tuck it away somewhere for travelling.
After I made this and had it finished, I discovered that the factory countertop had a warp in it. Crap.
So I had to remove about 1/8" on one side of the front support to make it sit flat.
This was a BIG brownie point winner (multiple points on this one) for the woman in my life....
Off to the right, you can also see a sink cutting board I made up from an ordinary store-bought one. I made a template and trimmed it to fit, sanded it down and added a finger hole. I also added a flip up counter extension at the far right which you can't see. Lotsa useable counter space now!
If you have a stove as opposed to a cooktop, you could do a smiliar thing. I looked all over the 'net for a factory made one that would work to no avail. The metals ones that fold just wouldn't work. You can't use them for a work surface.
If it's a wooden cutting board surface you really want, check out out www.countrymouldings.com
. They have a big selection of cutting blocks and wood counter tops and the best pricing I was able to find anywhere. Problem is with these is they are going to be at least 1" thick and thus heavy, being made from solid hardwood.