Don't know what your definition of cheap is. If you are looking to replace the strut assembly, it's going to cost more (around $100). If you're looking to for just a strut insert ($40-$60), there are few places that sell them online for a decent price.
Try:
http://www.intlautoparts.com
http://shop.auto-parts-zone.com
http://www.maximumautoparts.com
I think all the above have free shipping. I'm sure there are many more place. Once you get part numbers, you can call around local shops too. Sometimes you can catch a decent sale.