Don’t know what your idea of cheap is, but you could get a BLF Q8 for a “reasonable” price, and it will use four cells at a time. Be careful matching old/used cells. You want multiple cells used together to be as similar as possible in charge voltage, capacity, and internal resistance. If you have an analyzing charger, you could test your cells and match them accordingly. Now, having said that, since the Q8 uses cells in parallel instead of in series, the cell matching isn’t as crucial. I have cells from laptop pulls, and my method of matching is to check resting voltage with a multi-meter at least several days after a full charge. Cells with closest voltage get matched together. You can get by with this for two reasons only: the cells are known good quality and very well tested by the OEM, and the light is using the cells in parallel. If you’re interested, there is a thread about Lithium Ion cell safety HERE.