No personal experience, but I've read you can use Malta Goya (which can often be purchased in the appropriate section of the grocery store). It's basically unfermented wort. That may be what @Hello is referring to. But if DME is harder to come by than base malt, just make a large batch of ~1.035 unhopped, all-base malt wort, and can it in whatever size jars you see fit with a pressure cooker. That way you've got premade starter wort ready to go, just need to dump it in the appropriate starter vessel.