I have a sort of messy one I use for my own projects. It works great, I just never made it nice and neat:
download plugin here
download example cap here
it requires 2 objects in addition to the slider plugin itself
a slide the handle will slide on, which can be any object. I used a sprite in the example. it also needs a second sprite with drag and drop behavior on it.
it's very simple. the example cap has the slide at an angle to demonstrate that it works not only works horizontal and vertical, but at any angle. hope it's useful. I'd prefer to keep this off the svn, until some future date when it doesn't require a second object, but as I said, it works, and it's stable.
in start of layout: use setup slider: decide the two sprites you're using, and choose the minimum and maximum values you want the slider to have, and the starting value.
after that there is an action to update the value to the current slider position, and action to update the slider position to a new value that you specify (so you can move the slider around based on the value)
then there are expressions to retrieve the current value and the current 't' of the value, which is just a value from 0 to 1 representing where the handle is on the slider. depending on your knowledge of math, this is a shortcut that may or may not be useful to you