Before preparing a write-up about how to convert the cellphone charger for use with a 505 reader, I stopped by an Office Depot store to see if they had any more chargers in stock. I got one several months ago from them on closeout for $15 ($20 retail).
Well, I went in, found them and immediately bought TWO MORE Energizer chargers because they were $1 EACH!!!!!!!!!!!! It's worth $1 for the two lithium AA cells that are included. I'm attaching a picture as proof. If you're near an Office Depot, it might be worth a trip to see if they have any left. The store in San Carlos (California) had 2 more in the closeout bins.
The chargers are for Motorola phones, but I don't think it matters what phone, because they appear to all have the same charging unit, only different cables. The chargers all output 5VDC (I believe). In any case, Motorola phones charge at 5V.
More information about the Energizer chargers
here. I'll try to post instructions on how to modify the cell charger tomorrow or the day after.