If you're a good spriter, it's all about mimicking the style of the damaged sprites in the RTP. If not, you'd have to ask someone if they'll make one for you and that'd be asked in the Resource Requests section. If you're a spriter that wants a leg up to help you make them, check out how the RTP sprites look for damaged poses, gain some insight on shading, coloring, etc. and make your own. There's no generator for those kinds of sprites.