I understand that’s not the way you want to go anyway, but just as a reference for others perhaps interested … if you happen to have Fairphone Angels in your vicinity, they might be able to help you in person with something like this, it’s worth asking … 👼 The Fairphone Angels Program and Map (Local support by community members)
Fairphone mention the USB-C to USB-C Cable 2.0 as an option sold separately on https://shop.fairphone.com/en/buy-fairphone-4.
According to the details this cable supports fast-charging the Fairphone 4.
They also sell (or offer to include in a Fairphone 4 order, Thanks @yvmuell) the USB-C 3.2 Long Life Cable at a higher price.
While both cables look similar, the notable 2.0 → 3.2 difference should refer to the supported version of USB, where 3.2 would support much (much!) faster data transfer, so the 3.2 cable should be much (much!) better for e.g. copying files between a computer and the phone.
Else the 2.0 cable gets a “durable” in its description, while the 3.2 cable gets a “Lasts a lifetime”.
However @formerFP.Com.Manager, it is not mentioned here yet that the 3.2 cable supports the Fairphone 4, and the find a compatible charger or cable link on this page leads to a “Sign in to Fairphone” page.
If you only need the charger to somehow charge the phone, you can try any charger you already have first before buying a new one.
You just need a cable with a USB-C plug for the port in the phone, and the right plug for the port in the charger, in your case as in most cases USB-A (but there are chargers with USB-C ports, too, and chargers which have both).
The two cables mentioned above have both USB-C and USB-A (via the attached adapter part) on the supposed charger end.
You can even try to continue to use your old cable, you would just need an adapter for the port in the phone, in case of the cable you use to charge your Fairphone 1 it would be a micro USB socket → USB-C plug adapter.
If you want to make sure the charger charges your phone really quickly, you will need a new charger.
Your Fairphone 1 charger might still charge the Fairphone 4 reasonably quickly, but we just can’t be sure without both devices in hand.
Keep in mind that for the Fairphone 3/3+ Fairphone stress the importance of USB-IF certified chargers, and it turned out to be also important for cables.
If you want to try your equipment first and shop later locally, should the need arise and you want to save extra shipping costs, it might be prudent to watch out for USB-IF certification then.
If you use wired headphones with your Fairphone 1, the Fairphone 4 doesn’t have the jack for it built-in anymore. Here’s the official Fairphone adapter for this use case, but there should be generic ones in stores near you, too … USB-C to Mini Audio Jack Adapter (3.5mm) - Accessory | Fairphone.