I might have found it, but not sure if it will stay as it is right now for long (you know how it is in Shanghai, you wake up one morning to buy your milk at the local Lianhua, and it's a pet shop now...).
The place is quite hard to find because it's behind walls : do you know the Soho office building at the corner of Tongren lu and Nanyang lu ? When you're on Tongren lu, instead of turning towards Nanyang lu in direction of the Big bamboo, you turn in the small lane to go at the base of the Soho building, and you continue several meters on the left side : you'll find an empty and quite large parking area that connects to Changde lu. It is usually empty, but be careful : there are several trenches 20cm deep in this parking place, at least they were here 2 weeks ago. ;-))

I plan to go there when I get the bike, I'll let you know when. Tell me if you go to that place, and if it's still "available" for us. ;-))