Try contacting Ed Frias at EFE Speakers. Ed is a great guy and has done wonders with upgrading crossovers of some moderately price consumer level of speakers. You can contact Ed at firstname.lastname@example.org .
They made a center channel. Here is a link to audioreview.com classifieds where someone is selling a system including a linaeum center channel.
Thanks for the tip Btheaudiophile - unfortunately the ones in the ad you linked to are an even later version of the one I have.
After Linaeum went bankrupt, Radio Shack started making speakers with the Linaeum tweeter under the RCA brand. They even adopted a B&W-esque yellow "kevlar" woofer. It was very squishy and sounded pretty bad.
I'm thinking at this point that it isn't worth upgrading (it doesn't match well enough to justify the money) so I may have to sell off my beloved Linaeums and switch to something that does have a matching center channel - maybe the Maggie MMG's or somesuch.