Not sure which style L Seeburg is referred to here.  They actually
made two style L instruments that bear no resemblance to each other.
Here is suggestion for possible art glass replacement.

There are places around most major cities where art glass classes are
held and they are sometimes looking for projects for their students.

An alternate choice is the art class at a college or university.
I've sent a couple of friends in this direction when they needed fronts
painted on their band organs and they had beautiful work don't at very
little cost, mainly for materials.

Hal Davis