I was afraid you'd ask where I got mine simply because I got something akin to extreme mates' rates. For a whopping big $25 I got the whole kit: Yashica Electro GSN in mint condition, the tele converter and wide angle adapter (not worth spending money on, by the way), the Auto-Up (close up lens with finder), ever ready case and a hard cover case to carry it all in. Oh, and the manual. I bought it from a local antique dealer on the Mornington Peninsula (55kms south east of Melbourne). I haven't seen another GSN there before or since (this was two years ago) but he has had Ministers in there, if I recall correctly. I don't know anything about them to recommend that model one way or the other.
I won't be going out there any time soon (flat broke here), but I'll make a trip in a few weeks time and take a look for you and ask Jack (the store owner) to keep an eye out for one for you. I know what it's like to find what you're looking for but not be able to get your hands on it soon enough, so I realise three weeks is quite a delay! Sorry! I think he can be contacted by phone, if you'd like to give him a call. I'll go and look up their website's address and get back to you with more information.
As for the batteries, they used mercury batteries originally, but they'll happily accept a 4LR44 6V battery. Yashica Guy (at that first link I sent you) sells an adapter because these batteries don't come even close to fitting (narrower and shorter than the original), however, I simply wrapped a screw up in some aluminium foil and that works perfectly to ensure a contact at both ends.
I'll be back with that phone number for you.