I bought this second hand from the guy who bought a storage locker full of them. First thing I tried to do was to replace the stock / flat o-ring on the inner pump tube. Broke the small piston head!!! I'll try to fix it or remake a solution. As I know I'm not the only one.
Parting it out to recoup my expense. Tell me what you want and offer a fair price. It's like new condition.