PRUSA likes the bed to be cleaned with isopropyl alcohol. What else should I use?
Ethanol (Ethyl Alcohol) should work just fine as long as it's around 80% or more. It's very similar to isopropanol as a cleaning solvent. What you're basically doing is removing any stray grease from the bed with a solvent that evaporates quickly. 

Methanol would also probably work. It's very poisonous though, and shouldn't come into contact with your skin, so it requires a bit more careful handling. Methanol also has the benefit that it can't be used for hand sanitizer (since it's absorbed through the skin), so supplies shouldn't run out. 

Look for alternative sources, for example, methanol is often sold as de-icing agent for pneumatic brakes on trucks. Just make sure it's pure alcohol without anything funky added.