Hi
Walnuts are perfect for a hamster!
but make sure not to give too many to Toby, don't want him getting too plump
Chestnuts are ideal too, and the most popular nut for a hamster is a Brazil nut!! that was the only nut that my hamster ate, and it has a very good shelf life :P
But all nuts are highly fatty, so 1 or 2 nuts every other day or a not-so-often treat should be OK
Almonds are a nice treat too, but Toby may need help cracking the shell
The monkey nuts in the harry hamster food are safe, its only the shell thats a bit battered looking, you can crack open the shell and give the inside to Toby if the shell looks a bit rotten