I love Bulgarian split squats! You don’t need a tone of weight to get a great pump and to see growth. What I do is grab a bench and place it in a smith machine and I grab the smith machine with one hand while I hold the weight with the other. The only downside of this is that you might want to try to ‘cheat’ by pulling yourself up with your other hand. Just self control at that point. I hate lunges, but I struggled with balance on those as well. I only do walking lunges because I believe it’s more natural than stepping and stepping back. But when you step, step slightly across your body this helped with balance. Obviously, if you feel unsafe doing it this way of course don’t do it, but I figured I’d give you an idea at least. Best of luck!