It will be available in the Protovision shop:
You can register for the Protovision newsletter to get notified. But last time it was sold out in a few hours, so he didn't mention it in the newsletter. I sent him already 30 new cartridges, but he suggested that he will sell it again when he has 60, because then maybe it is not already sold out when the newsletter is sent.
I have already the PCBs for 100 more cartridges and I'm currently soldering the through hole parts and flashing the next 30, should be done in the next few weeks. I will write a message to this group as well, when new cartridges are available in the shop, but I'm sure everyone who wants one, will get one someday.