Thread for repairing convertible top?

[paqman]

I've got a 2005 Miata that the stitching has come undone around the back window in some spots, and I want to stitch it back up before gluing it from behind. Everywhere I read says to use upholstery thread, specifically polyester because of it's UV properties. But the only stuff in the stores locally is really thin lightweight stuff, not near as thick as whats in my top. The heaviest stuff I can find online is #92. I'm just not sure what I should be using. Can anyone recommend some good strong thread to use to repair these stitches? There is a lot of #138 nylon thread on ebay that says it's good for heavier jobs, just not sure about using it for outdoor applications. And it's hard to tell how heavy it is with the pictures online.