I use SciFit's BCAA 5000 Powder. You can get 1kg of it for pretty cheap. It's good quality, especially for the price, and I had no trouble maintaining strength or even breaking a few PRs while I was on GSD.
You can get fish oil anywhere. Walmart sells some cheap two-packs that will last you forever. I just bought 2 bottles of Biotest Flameout to see how the quality compares, but I can't speak to that effect just yet. I haven't had any trouble with the Walmart brands. You can take more to compensate for the quality of each pill, and I've only had one or two fish burps (and that was after drinking some diet soda).
Edit: Also, if you're going to be taking powder, learn from my mistakes. Don't try to mix it. Just get a measuring teaspoon, get a heaping scoop, put it in your mouth, and chase it back with something ASAP.