Thoughts on building your own spare tire?

Has anyone built their own spare tire? I know that a donut spare can be bought used off of eBay, marketplace, etc, but I am considering just getting a separate wheel (possibly cheap steelies) and a cheap, decent tire to go along with it. I'd hate to have to rely on a donut spare tire if I'm ever on a long commute with no tire places nearby. For example, I run a set of steelies with Blizzaks on them for the winter. I'm thinking of getting one more of the steel wheels and just fitting a decent tire on it. Any thoughts?

If you've done this, can you please share pics, fitment and other details of what you have?