A heat emitter should work fine. I use them for my rescues and rehomes on that size of cage. I have the back of the cage closed in with heavy clear plastic. It holds the heat in and you might find at times you have to close in an end as well. The clear plastic works great and is just about invisible. It comes on a big roll and you buy it by the yard. Walmart or fabric stores sells it. I use binder clips to attach it.
You must use a thermostat with the emitter. I use the ReptiTemp500R but there are other brands that work well too. Make sure you get the ones that have the probe that goes down to floor level and reads the temperature from there. These ones turn the emitter off and on as needed which is what you want especially when days get to be hot and nights are still cool.
I find an emitter to be a great option for those with one hedgehog. They are inexpensive to operate and don't heat the room up which is a huge plus for us.
You must use a thermostat with the emitter. I use the ReptiTemp500R but there are other brands that work well too. Make sure you get the ones that have the probe that goes down to floor level and reads the temperature from there. These ones turn the emitter off and on as needed which is what you want especially when days get to be hot and nights are still cool.
I find an emitter to be a great option for those with one hedgehog. They are inexpensive to operate and don't heat the room up which is a huge plus for us.