Portable battery anyone?

[Pamhad]

Does anyone know of a portable battery that will charge my Oneplus 9Pro? My old Anker doesn't even help it keep the charge it has when I am out and about playing Pokemon Go. I find the charge lasts about 4 hours or so while I am out and I would really really like not to have to switch to an older phone during the day so I really need a portable charger. It seems that Oneplus do not sell them (at least in the UK) and I have no idea if other brands/types will work. Would appreciate anyone who has a working portable charger letting me know the type/brand. All it really has to do is keep the battery alive for a day while I am playing

TIA

 

[tadpoles]

Here's one of a billion...

 

[Pamhad]

Sadly I can't get that in the UK

 

[A place on earth]

I don't have the brand myself, but Anker should be an okay. Though, I see it is an old thread, so what solution did you go with?