That is the same situation for me. That is, I would love to have one, but cannot justify the cost yet.

In that case, you are going to have to live with some distortion, and learn to compose the shot to reduce it.

By the way, renting a TS-E 17 here in the U.S. is $84 for 4 days. And a 6D is $59 for 4 days.