To save money, you can just use a syringe (without the needle, obviously!) You can buy an animal syringe (30cc or 50cc I think) for a few quid/dollars off Amazon or something. Just cut the end off, sand it down a bit and drill a small hole in the side. Cover the hole with your finger and use it with a little bit of lubricant and it works well as a makeshift pump. Just uncover the hole to release the pressure when you're done.
Obviously it's not as convenient 'cause you need to keep one hand in your pants but at least you won't be blowing $50+ if it stops working 🙂