You can play Moonstone on PC via DosBox direct via your browser here. It’s a great conversion in the main, though the music/SFX are a bit crap.
For the definitive Amiga incarnation of the game I recommend WINUAE. Courtesy of our Polish pals at thecompany.pl, you can simply download this tiny 5MB .exe file and play Moonstone in one click on your desktop, hassle free!
Kudos to thecompany for making life so much easier, and to Tavern pal Eric Cubizolle for giving me the heads up in the first place.
Tip: I personally managed to ‘break’ the game and snag all four Moonstones thanks to The Company’s Moonstone.exe. All you have to do is type ‘wepl’ (without the quotes) on the map screen to automatically get all four keys. Go defeat the Guardian, claim your moonstone – take it to the High Temple and flog it, re-enter the cheat and repeat the trick until you own all four.
If you still happen to own an Amiga, you can always hunt down an old copy of this rare classic at a car boot sale or from someplace like eBay. (But be prepared to pay literally £hundreds.) Likewise with the PC version, but you might get this one a little bit more cheaply. Only a little bit, mind.