There are many proxy services to help overseas buyers bid on Yahoo JP auctions. In particular; http://www.spe.bigbig.com/, Hajime/parachutes (firstname.lastname@example.org), and Hide (email@example.com / http://sharpservice.jp/ [which seems to be down right now]).I have used Hajime several times to buy mainly clothes and books online and have had no troubles.
I found and used a proxy service called Japonica Records, they placed my bid (on a Sunday), I won the item (Marble Sheep's 1st) and they will invoice me (Paypal) once they they receive the item - then post it on. They seem completely sound.
There's a load of Gerogerigegege 7" for sale on Yahoo Auctions Japan at a good price right now for anyone interested.