Why cant you use the 209m, or 209a primers for the 209x50. As long as you are not close the Max load for your gun?
Right now I am using 90 grs of pyrodex P 240 gr. 45 cal bullet and 209 m primers and have yet to have any troubles.
As a side note, today I found an unfired 209 m primer in the back of my truck it has been in it for almost 2 weeks trough rain ice storms and a bed full of snow. The primer was all rusted. I wanted to try and see if it would still fire out of my contender. took my empty gun loaded the primer and fired it. to my surprise it went off with about 2 inches of fire out of the muzzle (a 14 inch barrel)