That'll happen sometimes. Try different outdoor stores, and consider buying one of the really big bulk bags. The stuff they sell for potting houseplants often has fertilizer in it, but if you get those large 3.5 cubic yard bales of peat moss it's usually just plain peat. The larger ones are usually marketed more towards gardeners and landscapers so they assume that you'll mix in your own fertilizer. It costs more (usually $20 or so) but you get much more peat for your dollar - like 10 or 20 times, I think. I repotted my whole collection of Sarracenia and Drosera (at least 100 individual plants in all) with just two of those bales this year, and I still have a lot left over. Likewise, big bags of perlite are often just perlite, with no additives. If you can't find the right stuff anyplace nearby, try asking some of the lawn and garden staff if they can place a special order for you. A lot of the bigger hardware stores allow you to order stuff on their website and pick it up at a local store.
~Joe