Here is one you could try. Got a few golf balls, drill a hole through them, insert a length of string through them, lube them up and stuff as many as you can up your ass as you can. Im up to 5 now and going strong.
another is
Get your phone, put it on vibrate, silence it if you want. (I didn't which seemed a bit odd like the dinosaur in Jurassic Park with the phone after it eats the guy) attach a length of string to it somehow( You dont want to get that lost in you, put a condom over it and slid it up your ass slowly
then make a call to yourself and see how you fell about that. Iv tried it once and think I hit the sweet spot. I came real quick!!!!!
Mail me if you wanna share idea's..