Stuck on High Sierra

Looks like Apple has an endearing habit of removing software from its 
store that works on old systems, such as my mid-2010 MacBook Pro; of 
course they dictate both the software and the hardware.

Well, I can't afford a new one, so I guess I'll continue using bootleg 
copies; now, if anyone knows where I can find an old copy of GarageBand (I 
had it on Sierra, but it was somehow lost when I upgraded to High 
Sierra)...

Thanks.

-- Dave