Dear Samurai you have to get a small screwdriver and unscrew the screws that are on the side of the case,you take them out both 4 of them and you can change your strap.
If you cant get a new clasp from your dealer you could use any 22mm strap you like.You only have to source a set off 22mm spring bars.
Here the way how to change the strap.My photos are not that good but you get the idea.