Getting GP10 items might be a good idea, but you're already behind and farming under your turret, missing those last hits because you have no AD might hurt you more than it helps. Keep in mind GP10 items take at least 20mins to pay for themselves alone if you don't sell them (and 10 if you do).
Asking for help from the jungler is definetly a good idea, but even if you do get the kill you'll only clear a wave or so of minions before he comes back with even more items from all the gold he got off you.
Additional measures include giving golems to your top, trying to counter-jungle to make up for a bit of the deficit (especially effective if their jungler is breathing down your neck all game and is out of position to defend his jungle).
What I see happening in pro games when for example top is outmatched is they just give up on it. I mean no ganks, the guy sits under the tower getting last hits when he can, otherwise just trying to soak xp without getting hit/feeding more. The jungler tries to make up for it by ganking the other lanes instead and feeding his AP/AD carries, and once the top tower falls (and it will), the top guy will roam and try to help gank.
Keep in mind, after a point extra gold won't do much for you anymore. Once you have your core items, and a few "luxury items" as Dota players call them, the rest isn't as big a deal. If you keep playing and keep farming, you'll equalize eventually. Don't sacrifice more than you have to for towers, try to be aggressive about getting the dragon, and most importantly don't feed any more for any reason.