You might consider saving your own seeds. It's not too hard. Though hybrids might not be possible.
I tried San Marzano and they didn't do good for me. I find if I start my own plants I have better luck.
I'd decided once that to buy plants was easier than starting them but one year everyone got hit with a blight that was said to have come up from the south on the plants.
We have local growers who start them up here. Still I will start my own.
So far the seeds I've got are. Bonnie Best, Homestead and St. Pierre. These are the canning tomatoes I plan on growing. I'll grow others for eating, though I've been known to can anything.