Bruce,
To find a (temporary, or not so temporary) lid, you might consider heading back to the thrift circuit in search of a old dining room table. Many of these use nice chunks of hardwood for the top, and you might even luck out and find one with a suitable center-extend piece. Along those lines, some period, high quality shelving might also have sections large enough to trim for a lid.
Just make sure the potentional donor isn't worth more than the radio...
