Try PSI kits, click pen pkcp2400, or twist pen pkcp3000 or longwood bullet pen pkcp3800. All of these kits have rather plain clips. However, if his work place has problems with bullet type pens none of the available kits would seem to pass the test. The cap ends all have the rim of the casing showing and while in use the bullet tip shows prominently. Perhaps, another style pen would be more appropriate such as the bolt action tec-pen pktpen. Just my 2 cents.
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