Blu's battery is tip negative while the Janty Dura C , Mini Fogger, 501 are tip positive.
I checked mine with a meter. Can be bad news on the circuitry if you start swapping them in others chargers. Another thing to consider is the charging rate since Blu is smaller than the others mentioned. Charging to fast shortens battery life. A good circuit design should prevent damage with a simple diode if conected in reverse. As cheap as these units are, I wouldn't bet my stuff on it.
Blu has a nice little PCC that recharges 6 batteries before recharging the unit. A DPDT micro slide switch could be added so in one position it charged Blu normally and when switched it would reverse the power to the connector for the others that are tip positive. Could be done for about $3 in parts. The Dura, Fogger and 510 battery is a little larger so I'd expect no more than 4 recharges with them. I doubt the lid would close for charging as they are a little longer.
Even simpler would be to mount an atty thread in the case with the wires tapped into the Blu circuits output with that connector tip positive. No accidental "forgot to switch".
Just thinking out loud.........