Just look if you have a disk somewhere with an MSX game which also has .COM as extension to run it.
If the game works, then you know for sure you have those two files on that disk, since it cannot work without.
If you have not... get it. I can not point you to it here, but some creativity with Google etc. will get you there. 
The disk version of this game, for instance:
http://www.generation-msx.nl/msxdb/softwareinfo/674
has MSX-DOS aboard.
Get it, or, errr, buy it somewhere I mean, and you have COMMAND.COM and MSXDOS.SYS as well.
TASWORD rocked in it's time
It just needs MSXDOS.
Add COMMAND.COM and MSXDOS.SYS to a disk with this file and type SKMSX when in DOS.
And make sure you are in SCREEN 0 and not SCREEN 1, else it doesn't work correctly.
Amazing... there are still people over there using this program?
I have made it long time ago... in fact, the motivation was the PC program for DOS named Side Kick, which I used in the university (about 20 years ago).
The fact that it can be used only with screen o is that the code and the text are stored in the vram.
It could be ported to MSX 2 and use more memory, so allowing a large text to be worked, but I never had this computer, and now that I have (i have a small collection of old computers), I don't have the motivation...
Any way, try to get ge full package (skmsx.pma), which comes with some documentation...
Enjoy.
Roni.
xtor is the best with disk and VRAM text buffers
BTW i remember "e" text editor, which used only about 2K RAM for itself. Great piece of code.