Herr Kermit.... is it possible to make such a contraption?? 
You've got nothing to ein, zwei, drei, vier
As a device to let a MOSCART off, not too much trouble to build. As one to throw? nah, wouldnt want to do that for several reasons:
1: Solidity. Hell, I would *not* want to catch one on the head
2: Timer to set it off would be difficult to design, and even more difficult to "harden" sufficiently to allow it to withstand impact shock
3: Cost. 50 odd quid for a grenade, then a whole lot more to build the clockwork mechanism to set it off.
When we were a Kingdom it was run by a King
When we were an Empire it was run by an Empress
Now we're a country we're run by a..........
If you want stick grenades check this out at Airsoft World, (aka AirsoftScotland) 
http://www.airsoftscotland.com/acatalog/Fashbangs.html
Those are from TLSFX. I've met Tony from TLSFX (he's the "TL" in TLSFX) The blokes a nutter. And makes damn fine pyro 
When we were a Kingdom it was run by a King
When we were an Empire it was run by an Empress
Now we're a country we're run by a..........
I've got a replica heading my way from the US - just wondered if it would be possible to make it go "BANG!!!"
You've got nothing to ein, zwei, drei, vier