Definitely go to the trouble of getting some larger BG. In your situation I would much rather see you put in 20 six inch BG than several hundred 2" BG. The 6" BG will not get eaten and produce lots of fry (which still will likely get eaten too quickly if you do not remove some of the excess LMB) but the 200 2" fish would likely be 199 LMB snacks.
Dumping new fish in a pond is like putting a new kid in a tough school mid semester. The new fish do not know where hiding spots are. They are exceptionally vulnerable and likely at least somewhat in shock in what might be vastly different environment from where they came from.
Although your best bet is getting BG from a reputable supplier, in your situation if I could not find large BG from a fish vendor I would rather catch some larger BG and bucket stock them than wasting money on small fish that likely will not live more than 48 hours.
