How "ghetto" of a solution are you willing to accept? If you live near any sort of quarry or factories with large conveyor systems, you can probably get free conveyor belt material. I coach pole vault, and this is what we commonly use to create indoor vault runways. The material wears out for the purposes of conveyor belts long before it becomes unusable for running. It is plenty thick for spikes. If placed directly onto asphalt it will feel like a moderately firm all weather track.
I have also seen some frugal high schools get it to cover their track's straightaway during the off season so that the real track surface doesn't get worn as quickly.
I'm not sure what you would do about the turns.
Trying to cover an entire track this way would take many, many trips. It is also likely that you will have to wait for months or years as more material comes available.
But I'm not sure exactly what you had in mind. It could be a way to get you started, if you're just trying to improve on a bad situation. Maybe you could start with creating a single lane all the way around, if you're only coaching a small group at a middle school or something similar.
Good luck and let us know how it turns out.