I bought this pad in a nature shop, it's practically a cotton-made bag which is filled with some kind of seeds. It could be oat, or barley or wheat in my case, but I have seen them filled with cherry stones or corn (not the "pop" kind of corn!). They are very popular here but if you don't find one you can make it yourself. I found this great link (actually...Mike found it and put it among my bookmarks!) and I'm posting here some random pics to give you an idea of what mine looks like.
This one is actually sold here and it's really similar to the one I have.
These are made by Katie, check out her blog here she gives also awesome guidelines!
Katie's ones have vertical stitches which are great to keep the seeds more uniformly distributed but in that case you have to make sure not to overfill the sections or they can be a bit uncomfortable. Overfilling makes also the bag quite heavy and in my opinion not suitable if you use it with small children.
The one I have is not specific for babies at all but as it doesn't have vertical stitches I can shift the seeds inside to one side leaving the part which I put on Oliver's tummy a bit lighter.
If you make it yourself, have a look at the various seeds that you can use. My advice is not to go for corn or cherry stones as they are a bit too rough. Smaller seeds is the way to go! When I use it for Oliver I only warm mine in the microwave for a minute, then I shake the seeds to make sure the heat is uniformed and the right temperature. I'm going to add a couple of drops of lavender oil to the bag (after heating it) and see if it's even better! Do let me know how you get on!
Next on the list of things I want to get is a sling. There is such a variety it took me ages to learn pros and cons of them and make some sort of decision! I think I'm set on a stretchy wrap which apparently lasts a little less than a woven one weight-wise but it's easier to start with and a bit lighter. I have found a second hand one for a great price (Hoppediz brand) but I'm in love with a French one which apparently is the ultimate stretchy sling lasting as long as the woven ones (JPMBB do check this out the demo video is cool!) but way more expensive! Alternatively I like a microfleece one which I think suits Irish weather perfectly but probably not so much Italy (Calin Bleu brand). This one has the great advantage of being water repellent and very very light (and cheap!). Do you have a sling? Can you tell me how you are getting on with it?