I gave up on that idea because 1) there is not enough room in the boot and 2) my car has an LSD (a bad idea to mix undersized space-saver and normal wheel on LSD axle).
However in the boot there is now a plug repair kit as well as Mazda’s squirty goo bottle for two chances at a DIY get-me-home remedy.
Eventually I was also able to buy another wheel and tyre to match those on the car, but I keep this one in the garage, so that I need not be pressured by haste into buying a mismatched spare tyre or an expensive replacement wheel at premium prices.
The RAC is my final get-home card when all else fails.
I managed to get a Hyundai Coupe spare in unused condition for £55 off fleabay - luckily quite local so collection was ok. I’ve used it once - when I had a slow puncture and had to leave my tyre to be fixed whilst I went to work. On the back axle it was ok,( not sure it will clear the brake at the front and I’ve not tried it there) I just took it easy driving - when I collected my repaired wheel I didn’t have time to fit it, so just bunged it in the boot and used a bungy to keep the boot lid down on the short drive home.
For me a space saver is a lot more reassuring than a bit of sealant, and not too much money for the peace of mind. At the moment there’s a few on Fleabay, link below, but a bit too dear, keep looking out and I’m sure one will turn up at a reasonable price.