You could make something yourself if you have the skills to make something that'll work and last, but the average person here doesn't have those skills. The APC pack from Fry's is pretty worth it even if you DO have the skills, I think. 15 bucks for a good solid ready-made device from a reputable company.
And, being Li-Ion at 10Wh, it'll last much longer than those 2600mAh ni-mh batteries.
And, being Li-Ion at 10Wh, it'll last much longer than those 2600mAh ni-mh batteries.