Chemical Hair Relaxing

I have very unruly, wavy hair that is quite resistant to straightening (I am caucasian- Russian). I had it straightened in salons and it is expensive and sometimes reverts back to unruly in a few weeks. In the past few years I have done at home straightening using kits purchased from Walgreens and CVS. These can be quite damaging in trying to get my hair straight enough. I would be interested in trying one of the brands that were mentioned here- Rusk or Phyto. Where can they be purchased? I would prefer to purchase it in a store rather than on-line. Any suggestions for other brands would be great. Thanks.