Daniel Ockeloen is developing a grip extender for the new Sony A1II and Sony A9III . He writes:

As promised, an update on the design of the extender for the A1ii (and a9iii and probably a7V) I really want Sony or someone to make. This is now a fully working prototype: 17mm height, Airtag inside, Arca plate, Peak Design plug space, and easy battery swap. The Baby Extender Grip (BEG) is my way of begging some brand to make this. I am open to some people with 3D printers to share the files so you can test them. The core is now designed around an Airtag alu part from JJC .

The extender is compatible with popular Sony models such as the Sony A1 II , Sony A9 III , and Sony A7V .

He also made a special cooling grip:

Made a 2h22m 8k 25p 50hz, 520M 10bit 4:2:2 recording with my first test a1ii cooling grip. I just wanted to see if cooling in between the lcd and body would work. I think it can go unlimited in my test case at 20c room and no direct sunlight. I stopped it at that point. I also had to attach a usb bank to the a1ii because at 1h10m internal battery was at 10%. Did this because i was bored and well engineers that are bored start to fiddle and to provide feedback to Denz Ahmet . Ill report this back to smallrig sony design manager and maybe sony or smallrig or… will add something like this to their new cases as a option or build in. Canon made a 570 euro cooling grip for the R5ii that kind of does something like this and even this small test shows it could be done for the a1ii. I have no deep feelings if a a1ii should be used for 2hour 8k video thats up to people themselves and their usecases.

Cool project!