Brussels car dealer Jacques Coune built a handful of four seeater 122 convertibles, and one two-seater version. There are photos of page 37 of Anders Ditlev Clausager's book.

I own several convertibles (a Fiat 124 Spider, Fiat X1/9 (targa) and MG TD). They are very charming at first, and fun to drive around town in spring/fall. They are ghastly hot in summer, though. On the highway, you soon grow weary of the wind raging around you all the time. (Targa tops are relatively pleasant on the highway, though.)

One top type I have never owned, but I suspect would be more practical, is the "Webasto" roof. They are basically a giant sunroof, that opens up like 80% of the roof, with a cloth cover that opens in a series of folds toward the back. They are uncommon in the U.S., where I have seen them only on VW bugs. In Britain, they were very common, and made to fit many cars through the 60s. I saw a Volvo 123 GT featured in an article in Practical Classics a couple years ago. The car in the the article has a Webasto roof fitted, and it looked right at home on that car. (Sorry, I don't recall the issue, but Nigel Boothman wrote the article, and it was shortly after he joined the P.C. staff.)

I'll bet 122s with webasto roofs are a lot easier to find than convertibles! If you want to convert to a webasto roof, they are available, though I doubt they still make one for a 122. Here's a link:

http://www.webasto.us/press/en/am_auto_sunroofs_789.html

Here are a couple links to photos of a P1800 with a Webasto Roof:
From above:
http://volvo1800pictures.com/shows/darling03/Webasto%201.jpg
From below:
http://volvo1800pictures.com/shows/darling03/Webasto%202.jpg