This may not help for this year, but when planning ahead, a visit to a Target store in August-September for the back-to-school season will often turn up math workbooks in the $1 bins of seasonal items.
Another economical idea might be to make a DIY commemorative workbook: print a few
free math worksheets and
puzzles (
scholastic is another source) and/or previous years'
middle school and high school math talent search problem sets and answers, make your own customized, personalized, commemorative cover page (and a credits/sources page), to give the students a keepsake "workbook". The Do-It-Yourself approach may encourage kids to continue searching for resources on their own.
