As far as I know, there are a lot of such services on the internet, you just have to google, man. I have never made a DOS Attack, but I have a lot of experience in renting the
cheapest dedicated servers. However, if you have enough knowledge in that area, you can easily do it, it is very simple. I hope that you know that it is illegal and you can be sanctioned for that in accordance with your country's legislation. It's up to you, but be careful. Does it worth it ? In some countries, there is a punishment of up to 7 years of liberty deprivation.