i recommend using your own- not wasting money on pre-made---it is expensive.
you can puchase PFD fabric (prepared for dyeing) or
you can buy bleached muslin- pre-wash it to remove any sizing, chemicals or oils- use a mild detergent- no fabric softener- you are removing additives- don't re-add them.
then cut freezer paper the size of printer paper- iron it to the fabric- make sure your edges are adhered very well so they do not come loose when going through the printer- and --
there you go.
with the pre-made packages i have found it in packs of only 3 sheets and in packs of 10 sheets- both are expensive. i have used both- but found i got just as good of results (and in the case of one product my home made was much better)
make sure you are using an inkjet printer- it takes extra prep to use a laser printer.
after printing your pictures set them aside and let the ink dry (cure) i cure mine for 24 hours before heat setting.