Actually, you don't have to replace the tire kit. The compressor's perfectly fine for several dozen or hundred inflations - the manual states you replace the goop and filler tube only. The fact that a full kit costs $250 is because the dealer is marking up a $60 product to $250 like all dealers do.
You've got to realize this isn't a Smart part - it's made for Continental, the tire manufacturer, and then branded to Smart as a package. Any goop, any method of inflating, will inflate any tire. Remember, the tires aren't specific to the Smart. It's just a tire - and all forms of tire repair and replacement will work.