Ampeg Jet J-12 mod for preamp tube

I have a vintage J-12, but I can't find a 6bk11 for the preamp tube for the tremolo circuit. the other 6bk11 can be replaced by a 6c10 which is ok.

Any recommendations on modifying the amp to accept tubes that are commonly available? Its a wonderful amp, but I don't want to deal with finding obscure tubes for it.

thanks!

http://thetubestore.com/
6bk11 -- $59!

http://www.ebay.com/itm/6BK11-Amp-Tube-Ampeg-Jet-original-Hard-find-/220786557225
Used  US $99.00 

http://www.fliptops.net/catalog/product_info.php?products_id=399
"YOU CAN USE THE 6C10 IN IT'S PLACE"

As far as I can tell: 6BK11 is three-halves of a 12AX7.

And you can get 12AX7 in every age and flavor.

Therefore you kludge three 9-pin sockets in place of two 12-pin sockets, find pinouts for both, and wire HH for three sockets and GKP for each of of six sections.

6c10 is basically the same as 6bk11...

Too bad thetubestore.com is out, thats not a bad price.
$100 on ebay is crazy. I know there aren't many out there, but still...

A 6c10 doesn't work in the tremolo section of the amp, I replaced the other preamp tube with a 6c10. (I didn't just go off of the Fliptops.com info, I bought two 6c10s and tried them).

Where would I go about getting a case and male pins for a plug in adapter?