You could always use a picnic tap while you save for the tower. Also, do a search. There are several models that work well... sanyo was just the most popular. I got mine discounted due to it being discontinued, so they are prob going to be even harder to get.
Add up the cost of a tower, 5 lb tank, ball lock connecters, and a regulater. Then figure you spend that anyway... Either upgrading you wallyworld one or installing on the new one. Sometimes buying the right part once is cheaper than replacing crappy parts you already paid for