Is a product patentable that combines items available for sale in different products?

It is possible that the combination will be patentable depending on a variety of factors such as how long the craft kits have been on sale. The main issue is likely to be whether or not the combination is "obvious." The concept of obviousness is complex and has recently been re-defined in a Supreme Court case called KSR v. Teleflex. That case made it easier to find combinations to be obvious. Generally speaking, if you use components for something other than their normal use, or if there is some reason why it would be difficult or non-intuitive to combine the components (something that teaches away from the combination), you would have an argument against obviousness. You could read the KSR v. Teleflex case or discussions and come to your own conclusion, or see a patent attorney for advice.