Tanks of helium may be purchased from your local
Welding Supply company.
The most common size helium tank fills 244 cu.ft.
One of these tanks cost around $70.
To fill one of our 13' blimps (170 cu. ft.), for example, you would need one of
these tanks and would have plenty left over (74 cu. ft.)to top it off every 4 to 6 days.