You can download Xmas music on itunes (and I suppose other music sites).
You could get a burlap sack at a feed store or a home improvement store or a hardware store.
You can probably get a Santa suit from a costume store.
And you can get a real pine tree from a nursery.
If you have any thrift stores, you can ask the clerks if they have any Xmas stuff in the back (they stockpile it over the year and only bring it out right before Xmas).
A regular lighting supply store or even a home improvement store like Home Depot might have at least the white “fairy light” style Xmas lights.
You can string multi-colored paper chains out of construction paper and you can string popcorn yourself. You can also get some of those round styrofoam balls and paint them red and green and then hang the from the ceiling (ask the craft store clerks if you can use any type of spray paint, some of them the propellant actually destroys the styrofoam and it melts) but you can put them on a toothpick, stuck into another piece of styrofoam that you use for a base and simply brush paint them, but it will take longer.
You can also wrap “fake presents” in red and green paper with bows if you can’t find any Xmas design paper (just wrap empty boxes to use as decorations).
You can probably find some red, white and green pillar style candles to set around the room. If you can find any evergreen plants such as pine, cypress or even eucalyptus, you can cut off sprigs and boughs and put them in and around the candles. You might be able to find pinecones in bags at a store like Big Lots or Home Depot which you can also disperse in with the candles, or you can hang them from strings like the ball ornaments.
You can also string a bunch of those un-painted styrofoam balls on one string (and then have multiple strings hanging from the ceiling) to look like snowballs falling.
You can also cut out big “snowflakes” out of construction paper and either hang them or tape them to the walls.
If you have any big clear glass bowls you can fill them with tangerines or oranges and cinnamon sticks and sprigs of greenery, to give the room that Xmassy smell.
Thrift stores usually have a good selection of loose Xmas cards that you could punch a hole in the top and then string them up for decortations too.