Stock seems to be the trouble with the 5 series.
The silver ones even harder to get.
Richer sounds said they won't have stock for at least two weeks, so i wouldn't hold your breath!. I hope Nick Halliday will post to advise you further, i for one like it when companies(including Nick) respond on this forum etc. The Richer Sound price seems great, but everybody sells stuff cheap if they have no stock!
But at that price, may be worth waiting etc.
Av-Sales are awaiting stock on the silver ones, and i would highly recommend them for service. I have bought plenty of stuff from them with no problems.
Joe at the Media-Factory has always seemed very helpful, but only sells the black version. But i'm sure he does sell the silver Toshiba "Clone".
Sound And Vision Bolton, have black and silver ones in stock(came in today), but i don't know if these are pre-ordered. I bought the TH-42W5B from them today including a Keene syncblaster scart lead for my Sky+ digi box etc.