Here is a bag of 15A fuses I ordered from Mouser Electronics, a retailer for Littelfuse (the manufacturer). On the product label is a sample of the fuses in the bag (above) compared to a blown stock "accessory outlet" fuse (below), and again compared to a typical domestic mini auto fuse of the same amp rating (right)
These cost $0.32 a piece- and I expect that is much cheaper than you'll ever find at the dealer (if you can even find these fuses at the dealer). The manufacturer part number is 0897015.N (the last 3 digits represent the amp rating of the fuse; e.g. a 25A fuse would be 0897025.N)
Of course, shipping costs about $5.95, so you may as well buy a bunch of them if you need them.
The underhood fuse box should have fuses the size of the one on the right (with the extended fangs), but the fusebox beneath the driver side dash uses these mini blade type fuses.
Hope this helps guys,