There are a variety of voice changers on the market. Cheap ones are used in halloween props, and can be found at most party stores. Some of these sound a little like a Goa'uld, but most of them are too scratchy. I'm not sure if there are any good quality voice changers available, especially since a production like Stargate uses digital manipulation to change the voice after it is recorded. One thing to try though would be to get one of the cheap voice changers and wire in a better quality speaker.
The eyes ... yes, you can get light up contact lenses. Nothing with an L.E.D. though (they exist, but are only experimental at the moment). You can buy glow in the dark contacts, and they work really well. But you will need something to activate the effect. So you either need to be under a black light, or have a portable one. Ultraviolet L.E.D.s could be mounted to some type of headgear, and pointed at your eyes like spotlights. Then, with some type of switch, you could activate them at will and cause the contact lenses to light up at will. Since UV is outside the normal spectrum of vision, they shouldn't light up anything other than the contacts.
There's a video with some more information on the contacts
here.
UV L.E.D.s aren't hard to find. I bought a ton of them on eBay a few years ago. You will probably need to shop around to get ones bright enough to light up the contacts though, as many L.E.D.s are designed for low output of light.
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