It is normal to feel unwell if the colonic session has stirred up toxins. I would definitely get back and have a another session as quickly as possible to move those toxins out. I had a very similiar experience to you, but it was actually my 2nd session which made me feel quite unwell. I followed it up 48 hours later with another colonic and presto, mountains were moved, so to say, and I felt fantastic afterward.
An enema bucket will be fine, as long as you can hang it easily. If you go with an enema bag, get one you can fill from the top and that has the hose attached to bottom (so you're not constantly having to unscrew the hose to fill it). Look for something that will hold between 1500cc to 2000cc of water. You don't necessarily have to take all of it, but the more you can take, the better the results. There are several websites that have good quality enema equipment. I've been satisfied with Optimal Health. Some people add a small amount of soap, which increases the effectiveness. If you try this, be sure to use a mild soap like a Castile soap or Ivory soap, do not use detergents, liquid handsoap, etc. I have a minor neurological condition that has resulted in bowel problems, and have used occasional enemas for many years. They're about the simplest and most effective means I've found of relieving constipation.