You can use not only the 4k keyboard, but a 2k/3k keyboard with an adapter.
Any Amiga mouse will work, but a new one for just a few bucks (<$20) is good idea.
A 1084 is a better monitor for a toaster. You don't really need a flicker fixer.
And since the 4k has only one video slot, it goes to the toaster.
Where are you? I have been looking for a used (read cheap) flyer.