Different size shock cord:
http://m.rei.com/mt/www.rei.com/search?query=shock+cord&x=0&y=0&un_form_encoding=utf-8


Different types of cord locks depending on the diameter of shock cord you choose:

http://m.rei.com/mt/www.rei.com/product/848877/gear-aid-ellipse-toggle-cord-locks

http://cord-lock.com/ ... Never used them but it looks like they have any type of cord lock and cord end you might want.

You could also wander into your favorite camping store. All the bigger ones normally have repair equipment and shock cord and cord locks are normally stocked.

As an alternative to cord ends I normally melt the ends like you would paracord and use a double or triple fisherman's knot to secure the ends. You can use whatever is your favorite stopper knot.

Good luck.