Re-Routing to sydney IP

Hello,

We have 200+ users in our office. we are located in India. Our clients are located in sydney. We have Fortigate firewall in our office . We need to login with sydney IP in our office in India. Currently we have a fortigate firewall in AWS sydney region. From our local office fortigate firewall to AWS firewall we have created IPSEC VPN and created policy route in local firewall to set local users get AWS sydney IP.
But due to this the data transfer charges in AWS is getting higher day by day. Is there any alternate option available to reduce the cost or open source solution for this setup?