We just bought some halotron and foam extinguishers in the US last week. Just google
and you will find lots of places in the US that sells them. ProSupplyco.com is one.
Yes, the standard dry chemical extinguishers are about the worst type to have on a boat. They will put out fires, but you will probably be throwing out most of the electrical/electronic equipment
For small AFFF quick grabs around the galley
: Fire Gone 2NBFG2704 White/Red Fire Extinguisher - 16 oz., (Pack of 2) : Amazon.com : Automotive
Don't know about the USCG approval - I pay no attention to that when it comes to safety
. You can always keep the required number of cheap
dry chemical units in a locker somewhere for any inspection