I seem to recall a long discussion about left handed keyboards but can't find the particular thread.
The conclusion, IIRC, was that such keyboards do exist but are expensive.
However, today I've been thumbing through the latest issue of the Staples mail order catalogue and came across a Labtec wireless accessory kit which comprises a USB two button/scroll wheel optical mouse and a numeric pad.
Price of the kit? A very modest £24.99 + VAT.
Catalogue number is 7P-501 042 and telephone number is 0800 141414 (fax 0800 141516).