There is a large FRY's (Computers and Gadgets) not far from the Airport - thats probably the best place to look for gadgets & gear.
http://www.seattle.com/frys-electronics/
But the most amazing thing about the place? Every shop you go into has Scott Guthrie in it! No joke! (OK, not actual Scott Guthrie but there are an awful lot of people there who have worked extremely hard to master his speech inflections ...)
If you are lucky you might get a voucher to spend in the Company Store. Best value is software (hardware isn't discounted very much as there isn't that much profit on it in the first place).
Have fun.
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