There are lots of cars in the junkyard with lighter spare tire/wheels in aluminum.
I drive a first generation dodge neon and have done some crazy/tame things for weight reduction and weighed almost everything. These are all 5x100, is that what your Sunfire is? I saved about 9lbs going to a Sebring 15" aluminum spare. If you do grab one, there are two different kinds though. One is a little heavier, I can't remember if it was distinguishable from the lighter one or not. Just by a pound or two. All were only $12ish from the junkyard. Don't let them charge you the aluminum wheel price for the spare tire price. Luckily they are painted black.
OEM first gen spare, new condition 22lbs 11.3oz
OEM late 90s sebring convertible aluminum 15"x4" 5x100 spare new condition 13lbs 6.1oz
OEM late 90s sebring convertible aluminum 15"x4" 5x100 spare new condition w/o tire 9lbs 11.2oz
OEM early second gen 14x4" aluminum spare w/ lightly used tire 16lbs 6.4oz
There is also an aluminum one in some PT cruisers, although it seems uncommon.
You'll be able to see the marks left over from machining, it won't be perfectly smooth like the steel version.
Similar to these marks.
As a benefit it's also taller than the original to closer match the diameter of the other tires.
You can also shed some weight with the jack stand. The neon one is ~5lbs.
RX-7 Aluminum Jack stand 3lbs 2.8oz
PT Cruiser (and more?) Jack stand 2lbs 15.6oz
Pretty crazy that the PT steel jack stand was lighter! It does have a lot of holes in it. These are also cheap as well, but I think most yards remove them to prevent people jacking up cars and hurting themselves.
There are plenty of aluminum spares for all makes/models/sizes out there. Just takes some hunting in person or searching on the internet. Mainly on forums involving performance, a lot of guys run aluminum spare wheels with skinnies on a budget.