junkyard or a tire shop for second hand. tire rack or someplace on the internet for new. not sure if they do it anymore and i don't recomend it but sometimes you can find tires that have been recapped however i DON'T recomend this especially on a steer tire. recaps are notorious for getting hot and seperating and blowing a steer tire at 60 mph ain't a fun thing to have happen.
You have a computer, Check the local ads from the local tire stores and see who has coupons/discounts and so forth. I know that Discount Tires usually have a good deal going and carry inexpensive line of tires for folks who can not afford to get the best....Good Luck.