You can find them in the FASA Adventure Class Ships Vol. 2. Rather rare, but it is on eBay from time to time.
Altho we might want to also mention that the Adventure Class Ships 'deckplans' are in reality "battle maps", huge foldout square-grid battlemaps intended for Traveller tabletop miniatures use. In other words, we are talking about deckplans here that will cover almost half of your billiards/pool table. All told, these will cover an area of 17" by 22" or larger
Technically, they still are deckplans but..... I suppose the vast majority of Traveller players think of "deckplans" as a simple reference blueprint or SSD of a ship, examples like in Traders & Gunboats for CT.
Yes, the Adventure Class Ships boxed sets are gorgeous. Even if you never do Traveller miniatures, these are just gorgeous collector's items to possess. I think I have the boxes for ACS 1 and 2, not sure if I have Merchant Class Ships (if I do then I lost it). All from FASA.
** PPS --- ok I got my dusty boxed copy of ACS2. These are the ships contained:
Lord Somerset Class, Type M Subsidized Liner
Fanzhienz Class, Type A2 Far Trader
Kurgulash Class Medical Scout
Lady of Shalott Class, Type Y Yacht
Endeavor Class, SOLOMANI CONFEDERATION Patrol Frigate
(anyone interested in seeing a nice screenshot/jpeg of this RARE Solomani warship? Just ask me)
Lurushaar Kilaalum Class Patrol Ship
Stayaow Class Combat Scout
Alexandria Class Type A Free Trader
Eshpadir Class Orbital Facility
Explorer Class Survey Cruiser