I have sealed batteries (Not Gel) in all my bikes. Much better than the old flooded batteries. Pro cycle lists sealed batteries for the TW200. You'll need to get some foam to take up the extra room in the battery box since most are smaller than the stock battery. Also, fleabay list a number of Chinese made batteries for this bike. Beware though that some are made better than others with the weakness being related to flimsier positive and negative terminals. Scorpion sells a nice battery for the money and I've used many of them with great longevity. You can find a true gel cell for the TW but not sure its all that much better than a decent absorbed glass mat (Sealed) unit.