Hi Aboo,
We could use a previously discussed option here. Steps below
1) Get an extra private IP address from the same subnet as proxy
2) Add it as a VIP on the proxy
3) Create a Forwarding layer
4) Add a rule with destination field set as the domain you are concerned about
5) In the action field, use the "Reflect IP" option and give the VIP there.
Usage:This is to make sure that all the requests to that domain is sent by keeping the source IP as this new VIP
6) Add rules in your perimeter device to use one specific ISP link when the request is seen with the new VIP