Using the Subsidised Merchant as inspiration I get something like this:
Using a 400 Dton streamlined hull, it has performance of jump-4 and 2 g acceleration. There is fuel tankage of 170 Dton, enough for 4 weeks and jump-4.
The ship has a bridge with holographic controls. Adjacent to the bridge are a m/20 and a m/10/bis computer. The sensor suite include an improved sensor.
There are 19 staterooms, nine low berths, and five tons of common areas. There is an autodoc.
There are two turrets.
There is a Launch in a Docking Clamp.
Cargo capacity is 29 Dton. The ship requires a crew of nine: a pilot, an astrogator, three engineers, two service crew, and two gunners. The ship costs MCr 188,7.
Apart from the cargo hold it's basically a Subsidised Merchant so use those deck plans.
Special features:
The Launch is external, so the entire ship is 420 Dt: 400 Dt hull + 20 Dt launch.
A cargo crane system helps automate loading and unloading.
Fuel capacity is flexible: It can operate at J-4 with 29 Dt cargo, at J-3 with 71 Dt cargo, or J-2 with 113 Dt cargo. (A Demountable Tank can be removed to add another 42 Dt cargo space, decreasing jump range by 1.)
A computer m/20 can support J-4, the backup m/10bis computer can only support J-3 (but it's cheap).
A couple of turrets have been added; add weapons to taste.
Somehow an improved sensor suite (DM+1) and a decent software catalog has been added over the years.
Radiation Shielding gives extra protection against the hazards of space (and some weapons).
Repair Drones can help maintain the ship, perhaps they can replace one or two engineers if the adventurers are not that type.
In the Traveller tradition it's barely profitable, to encourage the crew to take side missions: