Good climber for mailbox?

My mailbox is located in my garden and I'd like to add a pretty flowering vine to climb up it and give some vertical visual interest. I'd like to avoid morning glory as the foliage gets too bushy for the idea I have in my head...I'm picturing a few nice, delicate tendrils of vine with flowers on them, not a big bushy covering. I also don't want it to take over everything (someone a few blocks away has some MG and it's spread down the street from her, growing in the sidewalk cracks, etc. I admit I do enjoy going past it as I walk the dog, but my next door neighbor would not be happy if I planted some and it spread to her beautiful garden!). Would clematis be a better choice or does it also get bushy and tend to spread? Is there something else you'd suggest for a sunny spot in zone 5b? The color scheme is purple, pink, blue, and white. Thanks :)

Some Clematis are now specifically bred to stay quite small, and even are grown in pots. I have never grown any. All of the full size traditional clematis I have grown get too big for your spot.
Here is a link to a small pink Clematis they sell at White Flower Farm.
http://www.whiteflowerfarm.com/26571-product.html

Another idea. I find that if given a chance, my Geranium 'Rozanne' climbs just a bit. I think it would be perfect for a mailbox, if you dangled a little netting or something for 'Rozanne" to hang on to. Rozanne blooms all summer for me.

Thanks for the ideas! The compact clematis might do the trick...I'll look into it further! I have a couple Rozanne and love them. Maybe I'll see about putting one under the mailbox and getting it to climb...might not make it to the top of the mailbox but it would be pretty climbing the bottom of the post. The purple combined with the pink clematis would be nice too :)

Here is a link to an old thread, about halfway through you will see a 2 photos of my Rozannes- In second photo- yes it IS the purple flower climbing up into the shrub behind the tree peony! I have found that given the chance it always climbs a bit. The first photo there, of it spreading below a clematis on a fence-this year it climbed up the clematis about 5 feet, super pretty. Here is a photo taken early August of the same spot.

Oh drat it loaded sideways. To see it in the correct orientation, just "right-click" on the photo, then click on "view photo" and it will open the photo in the correct orientation.

Thank you...I had no idea it could climb that much! Your link didn't come through if you are able to try again...I'd love to see it!

How strange, lately my links do not show up. Here it is again:

http://davesgarden.com/community/forums/t/1319558/?hl=

we planted a pink mandevilla in a pot at the base of mailbox post (buried it halfway) and it is beautiful, although you would have to do this each year. It is covered in blooms, easier to contain than morning glory