Ruth as said if you clean and flush the tank and lines with a clorine mix of 1/16 cp of clorine per 1 gal of water in tank.
Fill it all and run all water lines full and let sit for an hour.
Drain and then fill and flush whole system.
Now it should be safe from bactaria
I have a link to a site that may have any size tanks you may need.
polyramaplastics.com
Had the tank for my 79
Boler but never did get one and just use a 5 gal colapsable plastic jug but repiped system in camper so I can use just a hose if I am camping in a site that has water.