Ejaz
PBR won't help here because the IP accessing the web server could be any IP ie. internet.
So your switch has no way of knowing which ISP to send the traffic back to.
A possible solution is to NAT the incoming source IPs to a unique IP per ISP then you could use PBR to send the traffic back out the same way but most switches don't support NAT and it's not clear what else is in your network.
I think you may struggle to do this with the equipment you have mentioned.
Jon