how can I purchase IPs to connect to my VPS? also from where?
also do you know a place to offer VPN with dedicated IP ?

You need to get the IP from your VPS provider :) Only they can lease out IP on their hardware to you

And their ISP has to lease out the IP to them, only then can they give it out to you.

IPs generally, come in Blocks (5-10) and cost really cheap.