You can just use a spacesaver spare tire from any vehicle that has the same bolt pattern as long as the wheel fits over the brakes.
If you're just looking to save weight, you can also probably just get a 14" wheel and buy an inexpensive tire that fits on it, then use that as the spare.
In general though, you really only save a few pounds of weight, and a full-size spare tire has a lot of advantages over a space-saver spare, or even one that's just smaller.
You can drive full speed on the highway, and don't have to worry about taking it super-easy when driving with the spare off road or over bumps, plus it's just more durable as a regular tire, a spacesaver spare is just meant to get you off the road and to a tire shop to get a new tire or get the flat repaired.
One other thing you can do is just get a narrower tire with a taller sidewall on the stock spare tire wheel, so the outer diameter is the same as the stock tires. This saves a little bit of weight, gives more underbody clearance, but still lets you use the spare like a full size.
