I borrowed the pictures from
http://www.radioshack.com
Two different style fuse holders are available. I like the 'blade-type' better but it is just a preference. One is not better than the other.
On fuse holders the rating is the maximum fuse you can use. So, you get the 20 amp holder and use a 15 amp fuse.
20-Amp Heavy-Duty Inline Fuse Holder for 1¼x¼" Fuses, part number 270-1217
15 amp, glass fuse, part number 270-1073
20-Amp Inline Blade-Type Fuse Holder, part number 270-1213
15 amp, blade style fuse, part number 270-1082
I think the fuse holders just have plain wire sticking out. If so, pick up a package of Crimp on bu*t connectors for 14-16 gauge wire,
part number 64-3109
No soldering required.