I've seen an adapter that allows you to connect a regular co2 regulator to a paintball tank.
unfortunately that's all i have to add to the conversation. Other than to express my opinion that small co2 tanks are unreasonably expensive, so i feel your pain and all that. Me, I have a steel 20lb co2 tank which is bigger than is convenient and unreasonably heavy - but the price was right. Paid $100 for 1 keg, disconnects w/ flare fittings, picnic tap, and 20lb tank.