I have used a pad of 8.5 x 11 inch tracing paper at office supplies stores or Pat Catan's or maybe Michaels?;
You might also be able to get a roll of "canary paper" (pale yellow) at an art supply store that might be reasonably priced (haven't bought that in years!). That you can cut to size, but might have trouble in a printer.
Otherwise reg. copy paper (cheaper the better) with shortened stitch lengths.
Good luck.