NO they cannot take phantom unless they are modified. The batteries are not that hard to find for them. 3 stores had them locally here. Plus the batteries last a very long time. I have heard years in some cases. I personally wouldn't mod them unless you were using them daily and going through bats like crazy.
I just bought brand new ones for my set. They are Eveready #206
This is correct they can't take 48V phantom power. However they can be modified and there is a specific Nak guru in NM that does the best mods to these mics. LMK if you don't know who I am talking about and I can provide this person.
This 48V mod will lower the overall noise of these mics pretty drastically. Altough I never did have my 300's done I have heard the difference and if you plan on running these mics for a while you may wish to consider this. The mods are something in the order of $75 per mic and are well worth the upgrade. Not so much a matter of saving $ on cells, but to improve the sound/noise characteristics overall.
FYI - I used to get my 9V EV206's cells from Radio Shack, but they have to be ordered and take something like 3~5days. The cells should last you somewhere around 200hrs of continuous use.
Peace - LoS