seats for motor bikes

So I'm not a particularly fat guy . 6'+about 200 . But my seat keeps popping the spring out of the holder . It's a stock Dyno seat . I have a seat on my kent that has the rubber things that is real comfortable but I want something I little nicer . I really only want the pan and mount so I can...

I don't know about you but a bicycle seat just doesn't get it when you're going down the street at 35 or 40 mph. I don't want my back side hanging out over the rear tire. I want to get down in and have better control. I looked every where for such a seat for my 29er and couldn't find anything...