The reason that you couldn't find the 27% hydrogen peroxide is because at that level it is EXTREMELY DANGEROUS and could cause permanent damage and loss of all skin!!!!
Only under very very rare circumstances should it ever be used above 3%. The high grade, food grade, up to 30% is sold with the intention of industrial use or to be diluted down with distilled water to 3% and even at 3% most uses will require further dilution as needed. Look it up. See what could happen if one were to put 27% hydrogen peroxide on their skin. Fortunatly it is hard to come by and the few places that do sell it will usually instruct the user to dilute. But, to be safe, you may want to edit your posting so that someone doesn't get hurt.