I bought a house without a CF and Layout plan. 
The house owner is also a second hand buyer thus no layout plan and CF.
When I wanted to renovate, hired an agent who sourced the CF and drawn up another layout plan.
Cost Me Less than 4k only.
Should not be a big deal.

Buyer insist, just say 
"you want to buy this house, I sell, I don't sell CF and architect plan"

or in a nicer way 
"this house is sold without CF and architect plan, but if you insist, it can be sourced (hidden meaning- you want you go get yourself)"