Might consider doing in-RP purchases of individual ships, buying some old Gunships and Gunboats of various kinds off of whatever Freelancers and so on offer them in the Stock Exchange.
Would all be second-hand and not as easy as "dock and buy", but could work.
Your closest bet'd still stay the Tridente for that, and I don't see anything else coming up on the horizon, but then again I don't know your diplomacy too well.