Fairphone battery upgrade ideas?

I have a 65W 20000mAh power bank that auto-detects if the device is Quickcharge 4.0 or PD 3.0 capable. I bought it to charge my Steam Deck which takes 45W to charge while the handheld is in operation.

When I connect my FP4 I get 20W charging (9.5V / 2.1A) and can go from 15% to 80% in about 30 minutes. It sometimes throttles back to 10W (7V / 1.4A) depending on factors like battery temperature but it is still rapid charging compared to “ordinary” USB. I realise that it is pricey compared to some power banks on the market but I found it to fast charge anything I’ve connected to it.