Measure the inside width of the rim in mm and the distance from one locknut to the other on the hub (or distance between the inside of your fork dropouts (over locknut distance - OLD). Any 700c (622mm) wheel that is close to the inside rim width and equal to the OLD will work. Inquire with the merchant if either is not specified.

A wheel from a reputable dealer that insures the spokes are properly tensioned may be the cheapest in the long run, as the most likely reason your spokes broke was improper tension. A shop will likely charge $10-15 or more to check and properly tension a new wheel but the better ones may include that in the price.

Keep in mind that the appreciable store of knowledge in this forum in many cases comes from people who were or are employed at bike shops, and that your problems most likely arose due to bike that was not assembled and adjusted properly at a bike shop.