You might also try those doodads that are like a little blop of rubber cement.
You can attach a dual-sided adhesive tape yourself. Either put the eyes on the tape and then cut around, or lasercut matching circles from the tape.
I have seen 3M making some peel off adhesive blobs, but it seems far too expensive for affixing a .6 of cent googly eye to something.
There’s also that kind of contact-adhesive spray glue.
Put the eyes upside down to a piece of paper. Spray their backs. Place eyes to silicone-coated paper, e.g. the backing from paper stickers. Voila, readymade adhesive eyes.
Wil Wheaton’s wife Anne does this as well. I don’t know if they originated the term, but they use the term “VandalEyes” and she also set up a website dedicated to posting pictures of various VandalEyesed items.
Watch out, or you’ll end up with this.
I recently impulse-bought a similar bag of eyes. Thanks for the great tip.
Still going through a smaller bag I bought years ago.
Hint: I take those free refrigerator magnets and cut them into smaller size to fit behind the googles for steel. 
There are magnetic adhesive rubber sheets out there, used to turn any flat-backed object into a fridge magnet. You can use these.
Todo: find how easily the material laser-cuts.
Danger!
When I gave a talk at the Exploratorium, I was delighted to see a jar of googly eyes in the work room. Surprised that I didn’t see more of them deployed, though.
We have a couple pairs of the extra-large googly eyes, but haven’t been able to commit to an installation location.
In unrelated creepy-but-cool news, my local Rite-Aid is selling pretty dang good life-size skeletons. They’re poseable, with ratcheting joints so they can hold a pose, and their eyes light up to boot. Sticker price is $59.99, but with your Rite-Aid card they’re 50% off. I’ve been waiting for life-size skeletons at a decent price all my damn life! $30 is a screaming deal, you ask me.
So I… uh… bought five. 
Man, this is, in many ways, a WAAAY better time to be a kid, at least in terms of cool Halloween shit you can buy.
The top and bottom ones are cute! The middle one is going to give me nightmares. I think dinner is vegetarian tonight 
Glue them to your testicles and stand on your head.
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Oh this is amazing news. Gotta get to Rite Aid!!!
