The prices at Findatube are likely the best you'll find. That seller is well liked by the members of several antique radio forums. Type 45 tubes are unfortunately very expensive because they are in great demand by the tube audio fanatics.
It's too bad that you lost your set of tubes, because chances are that they were probably in good working order. Whenever anyone starts to repair an antique radio they tend to think that one or more of the tubes is most likely defective. However, it's far more likely that one or more capacitors has failed. The reason being that way back when tube radios were still very common, so were the replacement tubes. If it quit working, the owner could take the tubes down to a repair shop, test them and get replacements at low cost. However, if something else failed, most likely a capacitor, this was not repairable by the owner, and that's when they usually stuck the radio in the basement, not to be found until several decades later. So, when you find one of these old radios that's been in storage for decades, the most likely reason why it's non-operative is that a capacitor has failed.
Now having said that, even if the capacitors were still okay the last time the radio was used decades ago, it's virtually guaranteed that the electrolytics will now be bad, and most if not all of the paper capacitors will also be bad. You should not power up the radio without replacing the electrolytic and paper capacitors, or you'll risk destroying the power transformer and/or the audio output transformer. If that happens, then you may as well forget about trying to repair it, because replacement transformers will cost more than the radio is worth.