I would only consider a mutual conductance tester. TV7 is plentiful, and probably the entry level as far as cost is concerned. Built for military use, they are very durable. From there you can go up, up, up in cost.
It does sound like you had an output tube that shorted. To check for shorts in a tube, a tube tester is not required, a multi-meter would be sufficient. Good luck with the hunt.