I have a few thousand master images that have all the adjustments done with lightroom that I want to back up to a DLT drive.
DLT is essentially dead. Quantum may have a few mechanisms they haven't been able to offload, but LTO won the tape format wars 12 years ago. The latest LTO generation is LTO 8 but media only just became available again after the two worldwide makers of LTO 8 media settled their cross-lawsuits. LTO generally reads 2 generations back and writes 1 generation back, but LTO 8 is an exception.
If you're pinching pennies, you can get older LTO generation drives on eBay inexpensively and then you test them with the freely-downloadable diagnostic (for IBM mechanisms, that is ITDT) to make sure they're not junk.
If you're value-conscious, you can buy a rebuilt / tested tape drive with a warranty from a place like Midwest Technical.
If you have a lot of money, you can buy a new drive from any of the vendors that sell them (IBM, Dell, Lenovo, HP, Quantum, etc.)
Note that anything newer than LTO4 will be SAS only, so you'll likely need a SAS host adapter for your computer.