Some people have used hacksaw blades (with the teeth removed preferebly) for the spider.
They work well for the most part but are a bit thick for some. They also don't really have the height for best rigidity. They end up being about midway between what a wire spider is and a good sheet spider.
Personally, I'd go find some sheetmetal and make the spider arms a bit wider - something in the inch or more height is good. Use pins to hold the sheetmetal in the center and a pair of pinned clevis arrangements for the outer end of the spider.