Did you fill the body of the bubble counter with mineral oil? It slows the bubbles down so you can count them.
Make sure you put check valves before and after the bubble counter if you do that though.
For the OP, I have never used one of those, but I agree with Jaguar, just use a paintball setup or yeast CO2. A small paintball setup can cost less than $50 and only needs refilled every 3-6 months. Only costs a few dollars too.
When I can no more stir my soul to move, and life is but the ashes of a fire
When I can but remember that my heart once used to live and love, long and aspire
Oh, be thou then the first, the one thou art, be thou the calling, before all answering love
And in me wake hope, fear, boundless desire.