I bought 2 of these yesterday for $22. I think it was on sale as the price seems to have gone up a bit but its the same brand that makes Speign and I have purchased the same Speign case for every one of my Galaxys since the Note 4. A bit more than $40 but pretty sure it'll go on sale again my amazon price tracker says that its had 4 price changes in the last 30 days. It drops down to $20/30 every time.

It's a really nice battery, aluminum clad, 15,000mAh, 60W total output (2x 30W USB-C), 3 ports total 2xC 1xA and it supports 25W PPS for super fast charging. Puts out enough power to charge my laptop too. only downside is that it does not come charged, like at all. However it can recharge using a 30W PD charger.