Hey MES,
I have the one that came with mine. I lost the foamies awhile ago and used it without them for a couple of years before I replaced them (at $8 a pair!!??!!!--you know they cost 5 cents to make!).
I've tried the ear buds when I worked in-house and wasn't impressed.
Anyway, you can buy an adapter that converts 2 prongs to the standard plug. The one I found cost $30, but you could use any headset you wanted, so it might be worth it for you. Here's the link I found:
www.choicere.net/adapter/ (I just googled "dictaphone transcribers" plug adapter to get this link).
Also, if you end up buying one of the ones you referenced, you can get a better price by going to
www.transcribers.com and clicking "accessories."
Good luck!