You might find something close to what you want buying cheap Chinese RGB modules which are already built using dichroic reflectors to combine all of the colors into a single beam, turning them off and on individually but the power level you want is on the low side, that I have not run across yet.
Here's one rated for 200mw combined power:
RGB 200mW Stage Light Laser Module High Power White Laser Compact Design TTL | eBay
Otherwise, I believe you will probably need to buy individual low power modules and wire them together yourself using separate drivers for each diode, all running from the same DC power source.
I suppose you could buy the above projector and use it for parts to reconfigure into what ever you want to build. However, word of warning, some of these RGB-white modules don't last long, but this low powered one might, it's the ones they drive to their limits which fail quick and this is not a high power unit. You might also be able to adjust the amount of drive current to each diode to get the individual color outputs down to 20mw each. Check with the seller to see if the drive current to each diode is adjustable and how much range. Only problem with that is trying to communicate with someone in China who may not know English very well.
There is one China laser parts seller who sells these kinds of units who doesn't do too bad with communication, that is ebay seller Techhood, you might try looking at what he sells and ask him some questions. Buying from China isn't the best way to go, if there is something wrong returning the item for refund can cost more than the item itself, they can ship cheap to us, we can't ship back cheap. Because of that I recommend going to the google laser part store named DTR LPF. Just google "DTR LPF" to find his online store, he is in California.