I recommend the Heritage or NOW brands castor oil . both hexane free and cheap for the amount you get.
you can use any thing 100% cotton for the cloth pack in case you have a hard time finding un-dyed flannel as I did. I use baby cloth diapers 100% cotton and they work great plus super cheap if you buy a pack of them, perfect size to cover abdomen.
this treatment also relaxes you and brings so much peace of mind as you lay there for 30-60 min. I love it!