Most LCD's come with a thin sheet of crystal clear plastic over the screen. I, personally, have never seen a screen protector for a 28" LCD, however, that doesn't mean they are not available. Good luck!
saran wrap, fingernail polish, vasoline, carmex, or set a mirror behind the monitor and look at the mirror. honestly, though, i don't think putting a shiny cover over the screen will be the same as buying a glossy monitor. it'll just be a reflective surface over the matte cover over the screen, making it a strange thing.
If you want the gloss for aesthetics... then most of the above ideas will work. If you are thinking about modding it to protect it from children... Glass is your best bet. Actually attaching a sheet of glass (preferably automotive or 'safety' glass) would be the best protector. Any plastic material, regardless of gloss will become scratched over time from kids fingers and you cleaning it constantly. Glass does not scratch like that and is easier to clean IMO. Believe me, cleaning wears out plastic more than fingers.
Of course, you could just keep the monitor out of reach or make the kids stay away... I have two (5 and almost 3 years old) and I threaten broken-off fingers down to the first knuckle if they touch any of my lcds... lol.