I’m vegan and was on a fairly strict version of the diet as well (not diabetic, but I’m sure I had issues with glucose and insulin balance).
I did eat soy. If you read The Complete Candida Yeast Guidebook by Dr. Zoltan Rona and Annemarie Martin, they allow soy (organic, of course). And tempeh is better than tofu. Bascially, the same protein sources any vegan would have are available, as far as I can tell–the nuts may be limited to certain types, but that’s it. Quinoa is very high protein as well.
I did use some legumes and beans as well… mixing several together also worked for me. And even my snacks included some form of protein. I did post quite a few of the recipes on my blog if you’re interested in checking them out. For instance, a faux “chopped liver” (liverwurst) comes to mind–lentils, green beans and walnuts are the main ingredients, high in protein and just delicious.
And I think Zen50 has already mentioned some great sources!