You can try this mob for chain, I got one for a Greenfield, not sure if it was a 25H but you can give them the pin centers and the sprocket thickness and see if it fits, then get an extra joiner and just cut the chain to what you need,
http://www.ebay.com.au/itm/25H-152-...-Rocket-Quad-Dirt-Bike-ATV-/261085878301
