It would be difficult to approach for the refund personally. You can get services from a agency .
Residency certificate of company
Brief discripttion of company & purpose of visit
Original invoice for VAT claim
You can get services of U tax refund , an agency exclusively involve in foreign tax refund for all over countries & they work on no refund no fee basis If you get refund than they will charge certain percentage of your refund. Recently I have also taken their services for few countries.
Contact person at U tax refund - Mr. Neeraj Bagla(0999900373)