I live in the wack so buy mine at Animal House. Most pet stores that have the frozen food section carry Krill packs. Usualy mixed in the with Blood Worms, Mysis Shrimp, Brine shrimp ect.
It is used to feed larger fish so almost everyone that sells fish should carry it, can always call ahead and ask. Look at the packs before you buy one, sometimes there is some on the smaller side and you can sort through and find some packs that are larger krill, maybe differnt harvest times not sure but have noticed a difference and got little guys one time. Now i meake sure to look for the large ones.
Also can always just buy a 3$ pack of deli shrimp from any grocery store. Not the shrimp on the ring style, but deli shrimp you'll find in Chinese food (rice) and such. Little guys, they work farily well too when procured. Leave them to air out for a bit will help make them a little tougher.