How about an ISDT-C4? You should be able to get one for under $60. It is good for charging pairs of 18650s quickly. You can set the current anywhere between 0.1A and 3Amps per slot. Total charge power is limited to 25Watts combined.
The C4 does not have sliders. Cells that stray too far from the standard won’t work. It is limited to two 18650s or a single 26650. Short cells would need a DIY spacer. It can also charge 4xAA or 2xAAA but not at the same time.
For me, the biggest drawback is the single 26650 slot.
HKJ tested it but not with the latest firmware. The current firmware fixes some of the issues he reported.
