A little from outdoors is no big germ factory. If your worried about it then put it in a metal pan and bake it in the oven at 350 degrees for about a half hour...stirring occassionally. It will be dry and sterile.
There are always spilled or damage bags of sand at a home or garden center...take along a Zip Loc and ask the clerk if you can snag some off the ground/floor.
There are more germs lurking on your computers keyboard and your telephone than in a pail of sand...that is unless you're taking it out of a septic field.