Gold testers gel tubes drive me nuts

I think I purchased the original electronic gold tester the day they
hit the market. No more nitric acid, they were great. Many, many
years have passed and I think I’m on my third tester. The weak link
in all of these is the gel tube. I store them in the refrigerator,
religiously clean the tester after each use and still, they clog up,
leak and the plastic threads strip in the tubes. These are really a
pain. I have spent far more on these troublesome tubes than I have
spent on the testers themselves.

Can this magic goop be purchased in bulk and somehow do away with
these nasty tubes. What is your solution?

Thanks

Can this magic goop be purchased in bulk and somehow do away with
these nasty tubes. What is your solution? 

My solution was to discard the relatively useless tester (without the
gel, it’s useless, and mine was one of the first models, much less
convenient to use than current ones, with a reading that was just a
number you had to then compare with a chart.

I went back to using traditional test acids. A small bottle of
nitric, and another of hydrochloric. I feel in the amounts one is
using, they’re safe enough, and their shelf life (not unlimited, by
the way) is a whole lot longer than those silly gels. With practice
in the testing method, I feel the accuracy one can get is about the
same too. It Does, however, take some practice. the premixed acids,
already calibrated for certain carats, are easier to use, but I feel
they are potentially less accurate in some situations. I prefer an
actual comparison test on a streak of the unknown with a streak of a
known test piece of metal. Add some schwerters salts mix for testing
silver, and a bit of table salt for some tests (makes a very weak
chloride source when added to nitric, slower acting than adding hcl
to the nitric.

Peter