I checked out the site you suggested as well as some others. There appears to be adjustable angle trowels that will do the job. The only trouble is they are in the $20 to $30 range. I think I'll buy another $6 one for 90 degrees, and form it open for the 135 degree angle application I have. It shouldn't be too hard to do.
Thanks for the help,
Regards,
Dodgeman