I took a look at the SmallRig BMPCC4k cage 2203 and handle 1638. I was very surprised by the results with the cage and handle at an astonishingly low price of $88! Currently the cage is on sale for $69 (regular price $99) and the handle is $19. You get a total of 89 potential screw mounts on the cage and handle combined!
Once you have the BMPCC4k you either want to protect your investment with a cage or have a cage system that will allow modular options for a full and complete setup. Currently most cages are available for preorder and a few are on the market but I am sure they will fill your needs.
Not only will it boost the functionality by allowing battery, microphone, SSD, and other accessory mounting options but will give you a full on “professional” setup. The BMPCC4k transforms from a photography form factor to a cage system that can be rigged up for indie and Hollywood sets!
Here are a few of the cages that offer many options for the BMPCC4k.
By far the most comprehensive modular cage system, to date, is available from Tilta. They have not started to take preorders yet but once they do I believe they will be the go to cage for beginners and experienced BMPCC4k users.
Whatever option you choose, plan for the future and not just “right now”. There are plenty of other smaller cages and half cages but these are the ones that have great options.