Carry a spare. Simple as that. Motor home tires are not available at the corner 7/11 on Sunday afternoon. GS does not sell tires, does not stock tires and many of their contract providers do not either. If you don't have a spare, you are at the mercy of what is available in your area. Not GS fault at all if you are unprepared for a flat tire. If your coach came without a spare, get one. Or be willing to wait while one comes to you. That means next week some time in many cases. Not in an hour or so.
Carry a spare.