Just have him search 7v ac adapter on your countries Ebay and ensure the polarity on the head is the same as the fried one (and if the one you buy doesn't fit chop off the old one and splice it on the new one). The mA can be higher as the car will only pull what it needs, it just cant be lower but at 150mA I doubt you'd find lower anyway.
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Example search:
http://cgi.ebay.co.uk/AC-DC-MAINS-POWER-ADAPTOR-7V-0-3A-FE4116-070E030-SPN436-/260793524365?pt=LH_DefaultDomain_3&hash=item3cb881608d