I found this one listed on the Reverb auction web site for $2,420. Seller is Empire Guitars - here's the description:
"From Keith Richards to Greg Ginn to Dave Grohl the Dan Armstrong has been one of the most iconic and unique guitars around! The two most unique features of this incredible guitar are its see-through Plexiglass body and removable pickup. It was produced from ’69 to ’71 (there was also a short-run of them produced in the late 1990s and a second re-issue released in the 2006 but nothing beats the real deal Armstrong)."
"This Armstrong has a serial number of A877D and dates back to about 1969. The bolt-on maple neck has 24 frets with a rosewood fingerboard. There is a repaired crack in the back of the headstock that runs from slightly below the base of the neck up through the G and B tuning machines. It looks stabilized and does not seem to effect the playability. The tuners have been changed to Schallers; the B tuner is missing the back plate with the “S” Schaller logo. It is 24.75” scale with a replacement synthetic bone nut that measures about 1 9/16th”. The Formica “Fake wood panel” pickguard has a hole where the pickup selector switch used to be located. A washer from a Dunlop Strap Lock system is being used to hold the output jack sturdy. This particular example sports the original “RT Rock Treble” pickup, among the six options originally designed by Bill Lawrence (only the RT pickup is included with this particular guitar)."
"The Lucite guitar has an undeniable appeal to both classic rockers and died-in-wool punks, popping up in the hands of the guitarists of bands as varied as Unwound, Descendents, and the Melvins to Aerosmith, the Georgia Satellites, and Steve Miller. It has a good amount of weight to it (about 9 lbs 7 ounces). With the headstock repair and changed tuning machines this is a player’s grade Dan Armstrong, making it a great chance to get one of these super-cool babies without clearing out your bank account! It has been set-up by our in-house guitar tech for optimal playability. The body has some light-to-average wear but it is in pretty great shape for a guitar of its age. The Dan Armstrong Lucite is the perfect guitar for you to start acting out your rock n’ roll dreams and this is a fantastic opportunity to get one at a great price! Includes aftermarket hard shell case."