I have heard many different opinions about the G-spot orgasm. It depends on what you mean by spot. In my opinion, the whole debate about whether or not you can have a G-spot orgasm is a convenient way to sell a lot of books.
Some people have orgasms from having their ear lobes sucked.
I know people who can be reduced to jelly from having the back of their knees stroked. I'm going to write a book on the erotic potential found in the space between the big toe and the second toe, call it the Alexis spot, and wait for the checks to come rolling in. But that's not what you were looking for. You're looking for the urethral sponge. If you were looking at a vulva, above the vaginal opening, you would find the urethral opening.