Harbor Freight sells a set of cross bars for about $60. Which are exactly like the ones I bought from another place for much more. hindsight. They also sell a small rack that could be valuable. I put a rowing single on mine, much longer, but lighter.

It also depends on how far and fast you are going. If it were long distance on a highway, i would probably spring for a Thule. or similar. I have found the better racks do a better job protecting your gear and car, you are paying for that. There are many cheaper ways to carry stuff with less protection.