Simple, unbolt your top and replace it with another top with side windows in, locate all the bolts and undo them, lift the top from the front end until it is all loose, pull it clear of its two rear mounting pins and chock it with timber. With an assistant, lift it from each side and walk rearwards with it, replacement of the new top is a reverse.
Ensure you locate the rubber seal correctly over the cab section, as this can move when installing the new top, treat any scratched areas to prevent rust, and drop the top down in one movement. Takes about 30 minutes to swap tops.
Buy a top off evil bay, or someone breaking a vehicle, you can even get them the right colour for less than £100, check the operation of the sliding rear windows as these are prone to rusting on the frames.
Tops themselves are plastic, and quite light, these can be resprayed in any colour if required.