"With proper tools"
Yeah give me an injection moulder (well within the reach of a moderately determined modder these days, a lot of small board game companies will have their own) and some dies for it and you can have whatever you like. Alternatively if you wanted to get a lump of plastic of similar size to the case and mill out all the necessary plastic then you could also do that. Plastic is not that expensive or hard to machine but it does feel like an awful waste when I do such things.
More seriously I tend not to see off the shelf case mods like I might see for desktop cases and such, and with desktops then even the towers are standardised (ATX specifies where the screws go, how wide drive bays are and other such fun). There might be some for the various "gaming" laptops but it will be a model specific thing. Laptop cases are invariably all pretty custom to the model and maybe line of models that year. Space is usually pretty tight inside laptops as well, to say nothing of airflow, but if you go for thin ribbon cable or something you can probably tap off some power to stick some LEDs around the place.
Vinyl coverings are far more readily available as well, and even able to be custom made to order if you fancy having fun with measuring stuff.
