next time put a link to the item

the retroid pocket 3 measures
184.7 x 81.4 x 24.2mm (7.3″ x 3.2″ x 1″)

found the following ones 9"x3.8"1.57"
https://www.amazon.com/Hermitshell-Protective-Carrying-PowerCore-PowerPort/dp/B01DGK0ZDW/ref=sr_1_23_sspa?crid=1YQCH3OEA5U1T&keywords=Electronic%2BTech%2BZipper%2BBag%2BPouch&qid=1667448556&qu=eyJxc2MiOiIxLjUyIiwicXNhIjoiMC4wMCIsInFzcCI6IjAuMDAifQ%3D%3D&sprefix=electronic%2Btech%2Bzipper%2Bbag%2Bpouch%2Caps%2C92&sr=8-23-spons&smid=A6ALQ7NAGMPUT&th=1

this should be the "most" perfect fit
at Inner dimension 7''(L) x 3.5''(w) x 1.5''(H)
they have 3 sizes if you dont want the perfect fit "i think is a dice throw on the small counting for a lil bit more or could be less in those .3" then choose medium.
https://www.amazon.com/Compatible-PowerCore-20000mAh-Powerbank-RAVPower-16750mAh/dp/B09HYZCXQW/ref=sr_1_7_sspa?crid=U0KS72VSR3AK&keywords=Electronic%2Borganizer%2B7%2Binch&qid=1667448946&qu=eyJxc2MiOiIyLjExIiwicXNhIjoiMC4wMCIsInFzcCI6IjAuMDAifQ%3D%3D&sprefix=electronic%2Borganizer%2B7%2Binch%2Caps%2C84&sr=8-7-spons&th=1