The Sabre is a pretty reliable fighter for you right now as you're waiting for Junko to find information on Sinclair. You need to find a Concordia-class carrier, they're sold onboard and will last you all the way till Kusari, where the first planet in which you land sells the Thunderbolt. Also, I'll set things up so that you can buy the Bearcat in your first visit to Rheinland. Then you'll get the Lance on the Intrepid.
So, amusing bug notice: in the large setpiece battle at the beginning of Mission 10, the game seems to take some issue at the way I've configured the carriers, most likely in their collision meshes... cue spinning carriers that will kill your framerate and probably force you to reload from the last autosave a few minutes ago. Amusing, annoying but not entirely game-breaking, as I managed to get through that part. I'll revise the collision meshes to see if it solves the issue.
Good old times, isn't it?