Has anyone found a suitable 3rd party tube that fits and works?
You have the specifications from your original tube, then it’s just a matter of finding a brand that you like best. The length and diameter and of course the nominal power, these are the values ​​that are fairly similar in the industry.
You don’t write what’s wrong with your original tube, but sometimes it’s worth replacing the power supply for the tube at the same time.
I got my last 50W tube from Light Object in the pacific nw of the US.
You’ll need the tubes diameter and it’s length. The power a tube can put out is relative to it’s contained gas volume. Measuring a tubes diameter and length gives you an approximation of it’s power limits.
I got a 50W tube for my OMTech and it’s 1000mm in length.
The Gweike Machine Dimensions 38.2"*22.2"*9.2" (970mm*565mm*234.5mm), unless the tube is a much larger diameter, even a true 50W tube (1000mm) won’t fit in the cabinet of this Gweike.
A 60W tube is not only larger diameter wise, but also 1200mm in length…
Mine are 50mm in diameter, what is yours? What kind of current are you running?
I don’t change something out simply because everyone else dose. Many people say change the lps when you change the tube… I’m on my third tube, same lps. Tubes are costly enough, I just don’t replace things without a good reason.
Fortunately, you get to choose… 
Could it be that you are very unlucky with your tubes or how is it that you are at number 3?
I can’t imagine that with your theoretical knowledge of lasers, you would intentionally overload your tubes or run them uncooled. Do you have mass production or something like that?
I didn’t run it without anything, just at higher current levels. The tube must operate properly, so it needs cooling. Many of the articles out there suggest an 80% power limit. If I have a 50W tube I should be able to run at 20ma. I meet the maximum power output of 50W at only 15ma.
Any analog device will last longer if it’s run lower than it’s maximum.
Does this make sense?
I have always run mine at about 70% which is the point my tube peaks in power, that corresponds to about 16/17 mA. That is possibly why I am on my first tube on this laser machine yet.
(ps. only moderate daily use and some summer months not used at all)
Does that make sense?
Yes, completely. I know persons with K40’s that have had their tubes over 8 years… They have to be the most abusive on a tube.
I still think it’s biggest issue is it hot here a lot.
Be interesting to find the measurements of his tube.