Mel from All Wrapped Up shares a free pattern on her blog for making her Soy Envelope Clutch bag, with a couple of variations for the closure. The original tutorial shows how to make the purse with a bag lock. She follows that up with a second tutorial showing how you can add a magnetic snap. closure instead. Get the purse pattern and tutorial for the bag lock closure. Go to the tutorial for adding the magnetic snap.
[photo from All Wrapped Up]