The gold standard for g-spot toys is the stainless steel Njoy Pure Wand.
As pointed out above the Pure Wand does not vibrate. However my wife considers this may be an advantage. Without all the noise and having the vibe stimulate other parts of the vagina - especially the sensitive opening, she is free to focus exclusively on the pin-point g-spot stimulation that she gets from the Pure Wand.
My wife's advice is to make sure you void your bladder before you begin. The pressure on your g-spot will give you the sensation that you need to urinate. This is because the g-spot actually surrounds your urethra (it is sometimes referred to the 'urethral sponge' by some medical professionals).
Having emptied your bladder before hand - will enable you to confidently proceed, the urge to go will subside and you should be able to go all the way to orgasm. If you need a little help getting over the top - use your free hand and a small clit vibe like Mimi - the combination can be very powerful.