Jammaboards.com offers them with the -5vdc for an extra $20, but they don't to the service menu mod. I do both services for free as long as the sender pays for shipping both ways, I cover the labor. I'm not into this to make money. Just a hobby and always happy to help other gamers. I'm an electrician by trade, so it's no problem. I've done so many for free, that I can't start charging people now.
I am in Afghanistan right now and won't be home until July, so you'd have to wait until then, but I'm willing to help you out when I get home and when you get a switcher.
Oh, you can also get one from here...
http://arcademvs.com/ARCADE_ACESSERIOR.htm
Also, I noticed you need an MK1 board. I have 11 of them. 8 Y-Unit and 3 T-Unit. All complete kits. Let me know if you are interested.