I'm not so sure about unique Moz stuff, but Berwick Street, south of Oxford Street, has a number of independent record shops, one of which sells rare(ish) new Moz vinyl (eg 'Your Arsenal' and a selection of Smiths T-shirts. There are second-hand record shops there too.
Try the shop on the left in this picture:
http://images-eu.amazon.com/images/P/B00004WX1P.02.LZZZZZZZ.jpg
Good luck, I hope you can find something that you want. What do you want though? If you haven't got a copy I'd try to hunt down a copy of Jo Slee's book "Peepholism" if you wanted to treat yourself. Not exactly sure where you'd find one though.
> i'm traveling to london for the first time this week and i was wondering
> if there are any amazing record stores that sell hard to find or unique
> morrissey/smiths things? any help is appreciated!