SA:MP Client .ASI Plugin which allows to change connection IP address (select network adapter).
Copy samp-ip-changer.asi and samp-ip-changer.ini to gta_sa.exe game folder. (Make sure .asi loader is intalled)
Make sure you have configured dedicated network adapter to be connected to any VPN (e.g. free VPN for OpenVPN).
Take IPv4 address from adapter (it must be already preconfigured):
Open samp-ip-changer.ini and edit ip value (127.0.0.1 - default adapter: