Needle & thread
Sharpe knife for cutting leather
2mm drill bit
Leather punching tools
The leather came from ebay and was a handy 210mm x 295mm so mine didn't need cutting to size. A sturdy pair of scissors could be used to cut the leather depending on thickness but a knife can be cleanly run along the edge of a metal ruler to give a clean true cut.
I've made a couple of covers like the one above and think that leather of at least 2mm thickness works best.Metal
I've used aluminium sheet for the one pictured but anything flat will do! The aluminium is a couple of millimetres thick and has held up relatively well to the abuses of being in my bag.Leather punches
Can be home made from a nail, instructable to follow.