Yes, the second reserve is still available, and I'm glad it is.
I'll make a phone call to Maurice tomorrow, to make sure you get it.
It's best to have it exchanged, even though there is chance go repair it. I'm going to talk to Maurice about that too. Maybe I can get his permission that you 'd be allowed to attempt a repair, and get a replacement no matter you succeed or not.
For the repair itself, you would need to use a couple of very small wooden wedges, and use them to force the crack a bit open. If you're lucky, this can be done without separating the parts. Next, CA-glue can be dripped in, the wedges can be removed and a minimum of pressure can be used to make sure both parts are bonded together. Should the parts separate upon wedging, they still can be glued. After the time required to allow the glue to reach its maximum strength the hone can be lapped.
But as said, let me talk to Maurice first and see if I can get you a license to play, while he ships you the replacement. I'll tell him you're one of the world's most helpful Coticule experts, always helping out new guys with advice about their Coticule. That isn't a lie and he can't wish himself a better ambassador for the whetstones he mines and sells to make his living. I don't need to tell him that, in order to get you your replacement, but it might convince him to not expect the defect hone to return. Which saves you the shipping trouble and if you're lucky, gets you a spare Coticule.
Kind regards,
Bart.