Thriftier rhymes with:
heftier, loftier, altier, carpentier, cartier, chartier, cloutier, cottier, courtier, dirtier, emptier, flightier, fortier, gautier, heartier, heftier, loftier, meatier, meteor, mightier, mintier, mortier, nastier, palmatier, parmentier, peltier, portier, potier, prettier, rustier, saltier, sportier, tastier, trottier, whittier
Thriftier sounds like:
thereafter, tributary, troubadour, trovatore