The sound sampling on toys (raptor or otherwise, and yes, there was a screaming raptor Jurassic Park toy) is always horrible. Yes, you could dissect one, hook it up to an amplifier and a set of speakers, and get a loud noise, but it would mostly just sound like distortion.
All you need to do is link it to a smartphone, MP3 player, Digital memo recorder, CD player, Walkman, whatever, and hook that up to some battery powered speakers. The most you gotta build is a rig to improve the portability or concealment of the setup. If you're stuck using a Walkman or microcassette recorder (try to avoid microcassette, also has a lousy sound quality) don't just record it once so it must be constantly rewound. Record it on a loop a few dozen or a few hundred times or even fill up both sides of a tape with an appropriate pause between each playback. (Do I sound like a crazy old man talking about audiotape? regardless, they're dirt cheap these days).
Also keep in mind that "can be heard from 20 feet away" in a crowded convention center is a heck of a lot different than it is in a house with no one talking.