That sucks
What would you suggest then ?
Is the Ospho a better choice , I don't think it has Zinc or manganese in it like the Parkerizing solution
Would either set up a system to do it yourself, find someone you know might be kind enough to include them in his next batch or send/take them to a shop that does this sort of plating like the rest of us. Sometimes there is no short cuts or easy way to accomplish your goal