Austin Homebrew has a kit for the Fosters' Lager
... I've never seen the Fosters' Bitter in person, nor tried it, so I can't make an educated guess by taste.
But by simple style, I can take a wild in-the-dark guess. First, it's Australian. I've always heard that the "best" hops for an Oz beer are Pride Of Ringwood. Second, I'm guessing it's lighter in SRM than most, but not quite to the level of BMC. I'll take a wild guess and say about 6-7 SRM, that is, a nice darker straw, golden color.
Base malt, primarily. If it has any specialty malt in it, I'd say maybe 8 oz of Cara-Pils and 4 oz of .. uh, I dunno. Aromatic malt. Maybe not even that, maybe it's all base malt. I'd use Pilsner malt if I had to guess, but Pale 2-Row or 6-Row or whatever you have should be fine. This is all guessing, so it's not like it's going to be spot-on the first time.
OK so at this point I'm starting to stretch for ideas, so I popped open our friend BA and had a look
. Lots of talk about how it's "darker than they expected" so at this point, I'd say home-toast about 1lb of base grain, and use straight base grain for the rest of the bill. Target 1.037-1.040 tops. BA says 3.5% abv.
(If you're doing extract only, then you could probably safely stick to just pale DME or LME. If you want to pursue "toastiness", steep 4 oz - 8 oz of Victory malt or Aromatic malt, I would guess.)
Back to the hops, Pride of Ringwood is probably a good first bet. Pacific Gem could be interesting too, since tasters noted some very mild fruitiness. I've played with Pac Gem a bit, but not enough to really "get to know it". People call it "tobacco-y" and "woody" when used for bittering, and report that it's like blackberries when used for aroma hopping. Another interesting one could be the new NZ Green Bullet hops, they're supposed to be Saaz- or Styrian-esque in their subtle spiciness. I would probably go for about 20-25 IBUs? This is a low-ABV, low-OG beer, you don't need a lot of hop in it.
: Further reading, someone called it a "citrusy" aroma. Try NZ Riwaka hops. Austin Homebrew has them. They're Saazer-bred but have a citrusy nose to them. Again, keep the IBUs down to an appropriate level for your OG.
I realize this isn't exactly a recipe, as more of a guide. But it might get you close. That said, you might just brew up a standard English Bitter, see how you like it, and go from there.