Whey protein powder if you want
much better than soy. TJ's is very good & reasonable.
Post-workout you need protein AND carbs, the ideal ratio is 4:1 carbs:protein. Interestingly, chocolate milk (hot or cold) or chocolate soy milk have this ratio--it's a great post-workout drink. But don't buy storebought ones that are full of junk & corn syrup--make your own with quality unsweetened cocoa (like Droste) and sweeten to taste, you might try maple syrup. Turn it into a smoothie by adding some frozen banana chunks & blending.
Lowfat or nonfat *plain* yogurt or kefir are high in protein, low in carbs. I recently discovered kefir--an 8 oz serving is about 90 calories and 15 grams of protein! This is only for the plain--so you sweeten to your taste if you want. The flavored ones are very loaded with sugars and are much higher calories & less protein.
Congrats on your weight loss & good luck.