How can I get a 2019 TurboTax copy when I purchased it via a download? The computer it was on bit the dust

2019 software can no longer be downloaded from TurboTax.   2019 is no longer supported and cannot be updated.  

If you used desktop software downloaded/installed from a CD to your own computer, then the tax files are stored locally on your own hard drive or any backup device you used like a flash drive.  They are not stored online.  If you cannot recover them due to a hard drive failure, etc. you can get a free transcript from the IRS or for a fee of $43, an actual copy of your tax return.

https://www.irs.gov/individuals/get-transcript

https://www.irs.gov/pub/irs-pdf/f4506.pdf

Even if you find a copy of the 2019 TurboTax software somewhere, you will not be able to install it.