Well, you could at least upgrad to a 2/3A 6V NiMH pack. A 2/3A 5 cell hump pack usually fits in whatever area a 4xAA pack fits. Then at least your starting out with more volts. A decent 1500-1600mah 2/3A pack will give you enough run time for 1000cc's of fuel at least usually and be able to...
I think there used to be some name brand ones many years ago. I used to use the ofna micro ones, not sure if they monitor voltage or not.
Here's one that might:
https://www.amazon.com/BQLZR-Black-4-8V-6V-Nitro-Accelerator/dp/B00LVHGSIY
Your best option is to get a 2/3A NiMH 5 cell 6V...