Hi @manishv
Do you mean the lid cover or the top cover where the keyboard is located?
In any event here's the [https://kaas.hpcloud.hp.com/pdf-public/pdf_6940499_en-US-1.pdf|maintenance and service guide] for the HP ENVY 13-ba0000 Laptop PC ''series'' laptops that will help.
On p.21-25 Item #2 you will find the HP part numbers for all the top cover models available for the laptop series. They are ''country specific'' because the keyboard is part of the assembly so if this is the part you need, ensure that you find the correct one. Usually the part number can be found somewhere on the underside of the top cover if you wish to verify. As you said, not cheap.
On p.28 Item #6 (but shown as Item #8 on p.27) you will find the HP part number for the lid cover.
Search online using the required ''part number only'' to find suppliers that suit you best.
The manual describes the necessary pre-requisite steps and the procedures to completely dis assembly it, so that you can replace any removable part listed in the manual.
Click on the arrow to the left of ''Removal and replacement procedures for authorized service provider parts'' in the left column of the manual and then click on either ''display assembly'' or ''keyboard/top cover'' depending on which you need to replace.