More details on the antenna would help but I actually think I know the one you're talking about from Watson.
The ramtronix 800 MHz antenna is great, it's the old Radio Shack 800 MHz antenna made by GRE.
If I could recommend, the antenna that I use exclusively on my sds100, an antenna that I have had for many years and is hard to find, it's the Watson w-801. The REM 7-800 MHz antenna works fairly well on UHF but not so much on VHF High but the Watson gives me good performance on all three bands.
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I'm amazed the good performance I get on VHF High, UHF and 7-800 MHz.. I don't think this is the one that you are talking about as it is not limited to 800 MHz.
As finding it goes and where it's available is just a matter of searching Google in various different ways and see if you can find a vendor who still sells it. Check the company website.. HTH.