I have a tenant that has lost their keys and is requesting for the landlord to provide a set of new keys. Is this something that the landlord should cover or should the tenant provide their own replacement keys?
That's a good idea. I like that.
How could the tenant provide keys if they lost them?
If they actually have another set, they can go make them for a couple of bucks.
As JR said, I would do it for free this time and then charge a fee the next time it happens! Your tenants will appreciate the kind gesture and will hopefully not lose their keys again :)