Thanks everyone for the replies. I am trying to get an exact packed weight/size, then will get some more quotes from the places mentioned.
Chris, the lens is a single big solid piece of glass, so nuh uh.
Bernard, alas, I know noone on an air base or similiar. Will try to get international surface mail reinstated, but rumors of my influence are highly exaggerated. I will mention that Bernard C has been discombobulated, and hopefully the name-drop will have effect.
Will report back with a price comparison later, which ought to be useful to others.
And now just so you have something to gawp at, here's a pic of my new 3" square Berger "Lazalite" (tm) multiprism, in unused condition:

This isn't the piece I'm trying to ship, it's just the latest addition to the prism glass collection. It's a typical Selenium solarized "straw" color, which would date it to the 1920s, nu? Just after the Manganese era. Which reminds me, how
did they eventually solve the de-colorizing problem without just adding something to produce the "opposite" tint to
iron-greenish (which really produces a neutral "off-clear" instead of a true clear)? Pure sand deposits which produce clear glass are as rare now as ever, so how do they do it? Mn/Se both solarize, so do they just use something which doesn't? Rare earths?
--ian