I’ve a T350P/L and have found that the Targus Sport DVD case fits it almost perfectly.  If you put the T350 in it with the battery end up (toward the bag handles) it zips right up.  If you put it in there the other way it still fits but you run the risk of nicking the corners of the case on the zippers.  The front has a zippered pouch suitable for holding the power adapter, a small mouse a few other bits.  There’s also a slim pocket on the otherside suitable to tucking something thin, about the size of a DVD case for example.

If you’re looking for a cheap case solution from a place like Circuit City then this one’s worth considering.  I needed one quick to let my wife take this into work. 

http://www.targus.com/us/product_details.asp?sku=DVD301
http://tinyurl.com/bmbtd

I’ve ordered a VGP-CKT1 off ebay (from japan) so I’ll let you know what it’s like once it arrives.  Hopefully it’ll be compact enough to fit inside her briefcase without taking up too much room.