Having two partners simply gets all the lovely dopamine in your brain released in higher amounts and as a result you will be more aroused and your pleasure will be more intense. If your'e fellas are willing one thing that will blow the top of your head off is to have one of them penetrate you from the side and have the other one lick your clit simultaneously. You can also experience this double action in the reverse cowgirl position.

Here are links to two websites that will get you the third person for this fun. In the US try https://cowboys4angels.com/

In Europe try https://www.gigolo-services.com/escorts/mannen/

Though they have a couple of guys in the US as well DC and LA. I have used both agencies and can recommend them. Have fun!!