there are 2 very decent shields from drops [one being from botanica like mentioned before] and another quest reward shield from a chain in SMV [which i personally like over either of the 2 instance shields because of the block value :p] although the sha'tar rep shield would probably be the best out of any by quite a bit.
and hey, don't hate on the green gear, i had green champion gloves [stam/str/def] for months! i tanked all of kara / gruuls in them, until FINALLY i got maidens gloves [and of course, the random pug instance my friend asks me to help in drops thatias(sp?) self correcting gauntlets after i spend 20+ runs trying to get them]
finding him wasn't that hard
http://eu.wowarmory.com/character-sheet.xml?r=Khadgar&n=Gethol
get a new belt ... now. as well as rings, i'd advise you do TK instances, they drop a lot of nice tanking gear [esp rings... and a belt if i'm not mistaken] and gives you the rep you need to get pretty much the best shield you can get before nightbane.
also, don't focus on socket bonuses, after you get your 490 total defense, go for stam primarily. if its a one socketed item, put in stam/def IF it has a stam bonus, healers [and your raid group] will like you a lot more with a higher health pool later on =)
also, get revered with KoT [which isn't too hard to do] and get the tanking enchant on a helm, 90g isn't too much and the stats it adds are phenomenal :>
Edited, Sep 10th 2007 11:08pm by russki