A fun code challenge! I started with https://github.com/Alexir/CMUdict/blob/master/cmudict-0.7b as a list of words with pronunciation. It has:

  PIZZA  P IY1 T S AH0

Looks like I can search for " T S " to find the "ts sound that's not at the end"

  % grep " T S " cmudict-0.7b | wc -l
       991

Some of the non-proper nouns include ACCOUNTANCY, ANTSY, and ARTSY. I'll assume this is too close to the end to count, so require two sounds after the " T S ":

  % grep -E " T S [A-Z0-9]+ [A-Z0-9]+" cmudict-0.7b | wc -l
       853

These include: bestseller, blitzkrieg, boatswain, bootstrap, chutzpah, craftsman, draftsmanship, footstep, hotspot, itself, jetstream, outscore, outsell, outside, postscript, shirtsleeve, shortstop, sportsmanship, statesmen, tsar, tsunami, whatsoever, yachtsman, and zeitgeist.

(It doesn't have "spritzer" in the list, and uses the spelling "matzoh" instead of "matzo". I didn't look for a more complete list of word pronunciations.)

Finally, two words with two occurrences of the "ts" sound, neither at the end:

  % grep -E " T S .*T S " cmudict-0.7b
  ITSY-BITSY  IH2 T S IY0 B IH1 T S IY0
  TSETSE  T S IY1 T S IY0