I don't remember having a problem with size. This subject seems to be a minefield of double entendres. Anyway, if you go back to Amazon and find "sausage skins" in "Groceries" you will find a choice of sizes.
Not wishing to brag, but I found the process to be a two handed job and regret not paying a little more for an
electrical version, like so many things.
The best results I've had we're using Sainsbury's minced beef and pork and locally here in the north east Groupon keep sending me details of courses run by the Northumberland Sausage Company.