You could try the route add command at the following link:
Likely there is not a workaround, and rightfully so, it is a security feature.
Similar Juniper VPN clients will actually disconnect the VPN if an attempt is made to override by adding a route via the command prompt.
The reason this is done is to mitigate the risk of access to the corporate network via the remote user’s Internet connection.
Now on the flip side, it could be argued that you customer’s system admin has possibly not configured the VPN properly, as it is possible to route your traffic to the Internet via the corporate ISP and still maintain positive control of the traffic flow.