live yoghurt is available in your supermarket, my dogs love yeo valley.
probiotics, well yoghurt IS a probiotic, however if you want to give doses that are not diluted by the time they get to the gut then a multistrain probiotic from any health shop would be good; some need to be refrigerated, the micro encapsulated type are best.
FBO can be obtained from supermarkets or health food stores.
Personally I find Healthspan products to be of excellent quality and value and best of all they deliver! :D
They stock a wide range of supplements/vitamins etc and their service is excellent, they also produce a regular magazine.
http://www.healthspan.co.uk/shop/HTH