Buy the soundtrack. Or convert the video with something like clipconverter.cc for example or something that already converts to .wav.
Since I use clipconverter.cc I also have to turn it from mp3 to .wav, I use AudaCity or GoldWave for that but I recomend you using GoldWave as you can also put loop cues into the file which you will need. more info about loop cues here:
https://developer.valvesoftware.com/wiki/Looping_a_Sound
Also I recommend cuting the soundtrack. in the video the soundtrack is looped once, so it's twice as big as needed. Just cut it where it loops in your sound editing software.
Actually, because
I have nothing better to do I'm so generous I just did it myself. I cut the track once at 3:12 where it loops, and also at 0:54. So you have a shorter version to safe file size! Both versions will loop smoothly. I also exported both the full and the short version three times in 44100Hz, 22000Hz and 8000HZ. I dont know if they all work in Source and if you don't mind using lower quality, but they take less space! Also the 8000Hz version sounds like it's coming from an old radio so maybe it fits into the tf2 theme?
Here's the download:
https://puu.sh/xC7NH/01d0033465.rar You're welcome.
Contains 6 files:
shop8000hz.wav - 5.8MB
shop22000hz.wav - 16MB
shop44000hz.wav - 32MB
shopshort8000hz.wav - 1.6MB
shopshort22000hz.wav - 4.6MB
shopshort44000hz.wav - 9.2MB
Go to your tf folder and create the following path: tf/sounds/ilovelamp/ and put the files in there.
to play the files I highly recommend you to look into custom soundscape creation but we can go cheap with ambient_generics. Just place an ambient_generic where you want and at "Sound Name" you click "browse" to open the sound browser. filter for "shop" and select the sound file you want it to play.
Uncheck all flags of the ambient_generic so it will always play where it is located without needing an input first.