Want to buy an external memory mapper for nms 8280 (not megaram cartridge)

Probably from Padial Hardware, although I'm not sure about if he's still active, you can try to get in contact with him.

Padial's prices list

In that site there are lots of good hardware for msx i hope i can contact him!Doraemonppc thank you i will send you an email.One question though,does a 4mbyte memory mapper work ok?I have read somewhere that there are some problems with that much ram and that 1 mbyte sees to be better.So does it work ok with programs that need more ram?
Regards

Yes, it works fine.
I wans using it in my old nms 8280.
Now I have a turbo-r and I do not need it more.

I've also a Padial 4Mb external mapper and my only complaint goes to their shape. It's a very old model and it's even 2cm bigger than a sunrise case. Now, if I'm not wrong, they fit Konami cases.
The usual drawback is that some software (a lot of software in fact) doesn't recognize the external memory, ExecROM for example doesn't makes use of this kind of memory; but hey, SymbOS works flawlessly with the expansion!
Maybe 1Mb could be enough; but the 4Mb expansion seems a good purchase anyway...

@jltursan

The padial 4 mb mapper fits into konami cases, the later model cases that is. like pennant race one or solid snake (if you dare)