Some very common tube types are readily available anywhere. However, most of the tues in the 10B are relatively esoteric. If you do a google search on the tube type(s) you need, you will typically get a list of vendors. Then you can contact each of them individually. Antique Electronic Supply in AZ is a very good and very reliable source, for one. Then there is eBay.
If your 10B works and sounds good, I would not get exercised over the findings on a tube tester, most of which are even older than your 10B. Better to spend money on getting it aligned and let the tech tell you what tubes are not up to snuff.
If your 10B works and sounds good, I would not get exercised over the findings on a tube tester, most of which are even older than your 10B. Better to spend money on getting it aligned and let the tech tell you what tubes are not up to snuff.