The wiki says that Viper the Fleet is the master trainer for pickpocketing but when I go to him there is no dialoge for the training. This is annoying since he even asks if I want training when I first talk to him and my pickpocket is at lvl 91 so I can't go to the other trainers anymore. Is there any way to get him to train me again?

trainers cant take you above level 90, any of them.

EDIT:

All paid trainer stops training at 90.

Just save often, and start pickpocketing jewelry from the local populations.

Well this svcks, I got that far through hard work and wanted to be lazy for the last part. Time to reverse-pick-gold-grind for a while on a town guard.

You don't have much to be excited about anyway: it seems 90% chance to pickpocket = 75% chance of getting caught.
I still can't figure that one out.