Hi all, has been a while - gflorez contacted me and said there was still interest in the memory expansion, so here I am... I've been doing other hardware projects and have gained a lot of experince in producing hardware in quantity (using Chinese production facilities) and could now offer the internal memory expansion and SD card interfaces in large quantities.
I actually have one working and mostly complete SD card interface (the rewritable flash rom management needs completing, but that's just software). The reason I never built and sold any was the amount of work (and time!) involved in producing them. Well, this now isn't a problem if there is enough interest. I can also offer a case too, as I have a 3D printer.
I need to order 100 minimum per run, so if there is enough interest for the memory expansion or external SD interface I will look at getting them produced.
I have been producing an SD card based game cartridge for the Atari Lynx for the last few months and have had about 400 produced now, to give an idea of my production capacity.
I've started a poll above, so if you're interested in one or more items, please vote accordingly. If there's enough interest I'll get them made!