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I have the same problem, also I would like to get blue or red airtights. To place my colored strikes in.
However, I have not found ANY source for eather the colored factory Caps OR the airtights YET.
There is several collectors that has in the pass experimented with dyeing clear capsules. With so I hear--fair to good success. 1 collector on the clear cap, places a colored ring around the edge & the side of the clear cap. Of the strike that was in a colored cap. After placing it in a clear cap.
If you hear of a source of the colored caps. PLEASE LET ME KNOW. I would prefer the smaller older style caps, if possible.
Dan