Chookie writes:
I favour a climber over pergola too, but recommend strongly AGAINST
bougainvillea as it's both aggro and thorny -- not at all fun to cut back.

A passionfruit vine?

Morning Glory?

A cucumber vine? Those African cucumbers with the sharp spines like
to climb trees, and they are hardy. Very expensive if you can ever find
them in the greengrocer's, and you can scoop the contents out of the
shell with a spoon and eat that way, sweetened with sugar. Would need
a number of vines to get good coverage, I think. (Postscript: you're not
gonna actually sit in the pegola are you???? You might not want spikey
fruit dropping on your head. Wire netting over the pegola would fix it.)

If you are a thoroughly practical person, you might try a pumpkin vine.
There are some climbing beans that might do a good job of covering a
pegola, but you'd probably have green shield beetles dropping out of it.
--
John Savage (for email, replace "ks" with "k" and delete "n")