Where can i get a child's scooter that has a bike wheel at the front and two roller wheels at the back?

the make was 'Gladiator' the front wheel was about 16'' it had a tri frame and two scooter running boards at the back

The Gladiator was made by Schwinn who don't seem to make them anymore so ebay would be favourite for that.

Some other manufacturers make similar scooters though. Toys R Us have the Trikke 5, there's more about Trike products here:
http://trikke.com/

Hope you find what you're looking for.

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i think they were called "big wheels". try ebay

toys r us