With the exception of the M3 DS Real GBA Expansion Pack and Supercard (not sure why you would want one of these) you will be exceptionally hard pressed to find any of those.
Also my I ask why the M3 expansion pack when the 3 in 1 is still quite readily available and better supported? I am also not sure if it ever sold as standalone and my token search does not bring up much of anything, I am a few years out of buying flash carts though so that means very little.
The supercards we usually have to warn people off buying in the "EZ4 is rare as you like, where still has them?" threads so go back through the last few pages and you might find someone asking there.
Word on the street seems to be that a batch or two of EZ4s might be coming at some point if you want to watch the relevant threads for people to mention they have stock.
That chip looks like it is sized in megabits so you will need 8 of those which you will struggle to fit on a cart, not to mention it is VFBGA (Very Fine Ball Grid Array -- BGA soldering alone is a pain to do and VFBGA is going to be worse) in the form factors I saw which is not fun to solder (you will probably want IR for that). Voltages and currents do not seem to exceed the ones available though I would probably go for and I imagine 70ns is more than acceptable in the latency world. Searching for that they also appear to do SDRAM chips in 256 megabits and also better packages for hand builds, though they do appear a bit more power hungry.
Most flash carts do not use raw chips though and will instead use a CPLD or similar logic device to translate reads and such like. If you are just going basic ram pack then that should not be so pressing as the ones that get to manage 5 types of memory (loader, NOR, PSRAM, SRAM and something in the NAND world be it a chip or a SD/CF type thing) and multiple pages within those. Bonus with doing it that way is you can probably fake the presence of another cart and not have to recompile other homebrew for it (there was never a DLDI equivalent for RAM expansion packs so everything was compiled against and existing library or something like it) or write your own libraries.
I quote the first post because it's still your main question. I can suggest you one shop but it ships from Europe. I havn't found everything but maybe you will find something for you:
M3 DS Real with rumble Pack: Without or with RAM
This is the latest Slot-2 M3 I can find: M3 Perfect Pro Mini-SD adapter
I just find supercards with rumble any more.
Please remember, that they want to have some money for shipping and payment.
gamersection.ca is in canada and is reliable in sending the ordered item. It will cost you 10 to 20 bucks shipping but you will get it within 2 weeks.
eachmall.me is somewhere in europe so you shipping is going to cost you around 20 bucks or more regardless how little you buy. Shipping will take more than 2 weeks even with DHL world shipping.
As to what you want to call reliability in terms of being fast or not, they have both been fast at processing anybody's order on items that are on their hot list. Reliability in terms of customer service if you have a problem, it will be cheaper if you pick gamersection if you have to send back an item. Postal cost is cheap if your sending from the US to CA for your RMA.
[...]eachmall.me is somewhere in europe so you shipping is going to cost you around 20 bucks or more regardless how little you buy. Shipping will take more than 2 weeks even with DHL world shipping.
I just wanted to give you a heads up on this, eachmall.me actually ships from Hong Kong. eachmall.com is the main site, with eachmall.me hosting the same stuff as well as flashcarts and some other stuff like counterfeit Beats and fashion accessories; the former takes Credit card/western union (I think)/pay pal. The .me one only takes credit card and western union.
(I order _a lot_ of shit from them)
Also shipping on both sites is the same afaik, and it does scale up with how much you buy (relatively quickly though). Somewhat offset by the lower prices.