You can buy non-vigorous Clematis, as long as you shade the roots, also sweet peas do well if you make or buy a wigwam for them to climb up. Other clmbers? There are several annual ones - Lofos, Tropaeolum, Lobata minata, Rhodichiton, Cobaea scandens, Ipomoea, just to name a few.

You can only grow permanent climbers in a pot if the pot is very large, and the climber isn't a vigorous one, so only a few climbing roses would thrive, or a Jasmine beesianum, and possibly a Honeysuckle. My mind has gone blank at this point! Can't think of any more....