There's some nice soulful fiddling on "La Valse de Evangeline", and I'm wondering who it is.

Nice song. Sounds too close to Valse de Belizaire though.

Lawrence Walker d. 1968

The fiddler is his son in law, Merlin Fontenot. Still plays often as a pickup musician at Randol's. He is on all the Ambrose albums but one, where the fiddler is Leon Doucet. He also was on a couple of La Louisianne Nathan Abshire albums, and did some work with the Balfa Brothers, among others.

Son of a gun has some soul.

At the first Tribute to Cajun Music, 1974, with Ambrose Thibodeaux on triangle and Nathan Abshire on accordion

http://www.loc.gov/folklife/fieldwork/images/intro1.jpg

From a Liberty Theater performance with Jamie Berzas

http://www.lsue.edu/acadgate/Music2/misc/merlin.jpg

With Lee Benoit at Vermilionville, 1995

http://www.leebenoit.com/photos/musicians/jimmyleemerlin.jpg

At Randol's, 2003

http://www.leebenoit.com/photos/musicians/merlin1.jpg

Is he still around? It would be great to have a cd showcasing him.

Who all did he play with?

He's still around and playing. He did do a solo album some 24 or so years ago...it was on La Louisiane label and also features a great accordion player. The names of all the songs on that album are different but they are really the standard tunes like Lacassine Special, Hathaway Two-Step, Perrodin Two Step, etc. You might can still find it directly from La Louisianne. (just checked and I don't see it) You could email them and request info.
http://www.lalouisiannerecords.com/laloucat.htm