You can buy a tank of Helium from Ebay for $60 and a diamond shaped Optichamber for like $15.

@LukeAlmighty Current performance is never the issue. Dial the exercise in so you can do 8 but no more than 12 reps. 3 sets. When you hit 12 reps all three times, dial up by 5% and iterate.

If your strength is way down there, the bright side is that's a part of the curve where you can improve rapidly!