You can purchase your probiotics from any health shop. Be careful which one you buy as different brands vary in different strengths and qualities.
I found that the best brand is "Biocare". Is a bit pricey but you are assured quality. And they have their own website so you can wonder around and find the best supplement for your needs.
I intend to start on them myself but I cant afford it at the moment and I will continue to do a few more flushes until I see better results.