Edward,
there is more than one Helmstadt in Germany, and several Helmstedt's do also exist - do you have any more information?
As LDS lists several Streib's from the Heidelberg / Mosbach area, I assume the town you're looking for should be the Helmstadt about 20kms SE of Heidelberg in Baden, Germany.
As LDS has the protestant church records 1635-1962 for Helmstadt on microfilm, that would be a good place to start...
You can reach the town administration via email: gv-post@helmstadt-bargen.de .
The German phonebook lists one entry for Streib in Helmstadt, so maybe you could even contact her:
Streib Elke & Rösel Jochen
Flinsbach
Kornsgasse 25
74921 Helmstadt-Bargen
Phone 0049 (0) 72 63 6 42 28
Andreas