Obligatory "Not a woman, but" comment incoming. If you're very happy with your current vibrator it may be less that you're desensitized and more that you're bored with masturbation in general. If that's the case you'll probably find yourself in a similar position pretty soon after getting your new toy so keep that in mind as you're looking.
Do you have any interests or kinks that you could introduce into your routine that may provide for a bit more mental or intellectual stimulation perhaps?
I'll leave the actual toy recommendations to the experts, however my partner really enjoyed getting a Rabbit style vibrator that provides clitoral and g-spot stimulation at the same. It did take a bit to find the right shape that worked for her though because some were quite uncomfortable with the insertion.