5x7 enlargers have been made by any number of manufacturers. Some of the most common names are Durst, Elwood, Omega, although others certainly exist. My only experience is with the Durst which is a wonderful machine and came in a number of configurations. Check Ebay, as usual. They show up with some frequency. It's a buyer's market. Prices may range between $200 and $2000, but generally fall below $1000. Condition and location are the usual deal-breakers. Whatever you do decide to get, make sure it's complete, i.e., with negative carrier, condensers, baseboard, etc. Spares are available, but you can spend as much on a negative carrier as on the whole enlarger these days.