Hardly possible with windows alone, easiest way would be to use a virtual machine (eventho you said no VM), you'd just assign a vNIC (Virtual Network Interface Card) to your VM that is different than the one you use on your host.
For example:
host uses NIC 1 and VM uses vNIC1 which is mapped to host's NIC2 (assumes you have 2 NIC in your computer)
or
host uses NIC1 and VM uses vNIC1 which is mapped to host's NIC1 but VM uses a VPN aswell, successfuly separating your two clients on different IP.
Using VMWare Player (which is free) you could use a VM to accomplish what I described in this post. One problem is that VM Player doesn't allow you (as far as i know) to create VM yourself. I do, however, have a license of VMWare Workstation, if you'd like I could create a Windows VM for you and upload it to like google drive and then you could download it and start it with VM Player, for a small fee.