check "native seed search " tucson AZ . FOR THERE wild type tomatoes .
Also remember that cold tolerance and drought tolerance are closely related . so try that strain that was developed for Greenland , Siberian varieties and check www.ARS-GRIN.GOV for varieties.

HOMESTEAD can take the heat'thats one of it's features

I know these aren't tomatoes, but cousins...try Tomatillos!

Vera

If you're still looking...

I have had good luck with Spanish-sounding varieties. They might be Italian or Mexican - who knows? In particular, Muchamiel, Rio Grande, and Tres Cantos did real well for me this year. They are smaller and not quite my preffered flavors, but they will produce for you. At least they are bigger than cherry tomatoes, which grow under any conditions...