I never purchased Garage Band for High Sierra 10.13.6 and now I would like to install it

I recently was given an iMac mid 2011 27" with an Intel i5, 1TB HDD and 32 gigs of ram. The computer is in brand new looking physical condition. I erased the HDD and reloaded High Sierra 10.13.6 with all available updates.

I would like to purchase or download any option available for Logic Pro X or Garage Band to use on this machine.

Searching online has resulted nothing legitimate for a download other than scam websites. I looked on Amazon and eBay for an iLife 11 disc, I see some available but have read that if the disc is not the version specific the machine it won't load so I don't want to take a chance.

I contacted Apple and was told they cannot help me because the version I need is no longer available. Does anyone know a reliable source for me to locate either of these applications? Thanks RS